1. If you have a Windows computer, you must obtain and install all of the following: a reputable antivirus program, a software firewall, a junk-mail filter and an antispyware program. Even if you own a Macintosh (Macs have been unaffected by most of these threats to date), you will still need to turn on your computer’s firewall and employ a junk-mail filter.

2. Upgrade to the latest versions of the leading Windows web browsers, Microsoft’s Internet Explorer 7 and Mozilla’s Firefox 2.0, both of which warn you when a web page you’re visiting appears to be phony. (The new Internet Explorer also has under-the-hood security improvements that close some of the holes plaguing older versions.) You might also consider add-on software, like McAfee’s SiteAdvisor or the new Norton Confidential, which warn about fraudulent sites and, in the case of Norton, also about malicious software on your PC. On a Mac, consider using Firefox 2.0 instead of Apple’s Safari, which, while very good and generally secure, lacks a fake-web-site detector.

3. Never respond to or click a link within any unsolicited email message from a financial institution — even your own — no matter how official it looks. Crooks have become skilled at mimicking logos and typefaces used by banks, brokers and payment services like PayPal. When you click on links within these fake emails, you’ll be taken to web pages that look like the companies’ official sites, even down to the address, but they’ll steal your log-in information. Be especially wary of email from a financial institution that asks for account information or says you must log in at a linked site to address a problem. You can phone the company to see if there really is an issue. Obviously, this caution doesn’t apply to some financial emails, such as confirmations of online stock trades you’ve just executed. But in general, you shouldn’t conduct financial transactions via email or links in email. Instead, go directly to the financial sites you use.

4. Similarly, never act on emails offering stock tips, miracle pills or the chance to earn money by storing millions from overseas in your bank account. Sounds obvious, but in the past these scams might have cost you a little money. Now they may be part of more-damaging identity-theft schemes. Treat such come-ons the way you’d treat a stranger in a bad neighborhood who made such promises.

5. Never, ever download software from a company or web site whose honesty or veracity you’re not sure of. If a site says you’ll need special software to use its features, don’t bite. Even if the software is well known and safe — like RealNetworks’ RealPlayer, Apple’s QuickTime or Adobe Flash — don’t get it from a link provided by a random web page. Instead, visit the Real, Apple or Adobe sites to download it manually.

6. Finally, never use security software offered to you via unsolicited email or a popup window, or that suddenly appears on your PC. Such programs are almost always scams and often install malicious spyware, adware and viruses rather than cleaning them up. In general, stick with leading security brands like Symantec, McAfee, Zone Labs and Webroot. Check the software in the reviews section of PC Magazine or the CNET web site. If it isn’t covered there, it’s probably untrustworthy.

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about watching Major League Baseball’s streaming Webcasts of games, the capacity of digital music players and the security of Wi-Fi.

I just bought a new Mac and I love it, but I am a die-hard Yankees fan and I find that, with the Mac, I can’t watch Major League Baseball’s streaming Webcasts of games. Is there a way around this?

Since I am a huge Red Sox fan, I hesitate to help you … but I will.

It doesn’t work, because MLB.com this year switched to a Microsoft video format that the Mac version of Windows Media Player can’t handle and it doesn’t support the Safari Web browser that Apple includes on every Mac. There is a workaround: download and use Firefox, instead of Safari; and download and install Flip4Mac, a free program that allows QuickTime to handle the newest Windows Media video format. You can get it at: http://flip4mac.com/.

But even this solution is seriously flawed. The problem — and the Flip4Mac people are working on it — is that it plays only for a few batters or so, and then you have to restart it by relaunching the TV feed in the Web site. This is a pain, but it does work, sort of.

A better solution is to simply run Windows on your Mac, and then play the MLB videos on that. I do this using a product called Parallels desktop, which runs Windows inside a window on your Mac. It’s available at: www.parallels.com.

I am not clear about capacity on digital music players. As far as I can determine, most music CDs run to about 600-700 MB, so a mere 10 CDs would fill most of a 10-gigabyte iPod, correct? On the other hand, I recently read that all of Mozart’s works would fit on a 10-GB iPod. So what’s wrong with my calculations?

When companies calculate the capacity of digital music players in terms of songs or CDs, they base their calculations on the use of music files that have been drastically shrunk from their original size on a CD. This is done by converting the songs to compressed file formats, including the MP3, WMA, or AAC formats. This is what happens when you import, or “rip,” a CD into iTunes or Windows Media Player on your computer in preparation for loading the songs onto a portable player.

A typical MP3 file compresses CD music by a factor of 10 or more. So, a 650-megabyte CD might take up just 60-65 megabytes on a computer or a portable player. There is a price to this compression: The quality of the music file is degraded. However, most people find the quality acceptable, especially with common types of music — pop, rock, country and hip-hop.

Many audiophiles and classical-music fans choose to compress their CDs less drastically, seeking a balance between space-saving and quality. This can be achieved by changing the settings in your music software. Others opt for no compression at all, though, as you noted, that severely limits how much music you can squeeze onto a portable player.

I would like to link up the computers in my home wirelessly but am apprehensive about the security aspects. Is it safe to use Wi-Fi?

Yes, in almost all cases. Wi-Fi networks come with an optional security feature that requires anyone using them to know your password. So, you can turn that on. Even if you don’t, your files would be at risk only if you had a neighbor close enough to access the network who is both skilled enough and nasty enough to want to poke around in your files. In most neighborhoods, that combination is pretty rare, as is the likelihood that hackers will drive down your street in a van with a laptop and steal your secrets.

However, I would also maintain a software firewall and turn off all file-sharing features of your operating system and other software.

There are exceptions. If you live in a large apartment building, the number of potential snoopers who are strangers goes way up, since many more people will be close enough to access your network than they would be in a suburban neighborhood of single-family homes. Also, no security system is perfect. Determined hackers could theoretically break into any wireless network.

But, in most scenarios, I believe Wi-Fi is safe.

* * *

Because of the volume of e-mail I receive, I can’t routinely answer individual questions by e-mail, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

• Write to Walter S. Mossberg at mossberg@wsj.com

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about speech-recognition software for Macs, whether Windows Media Player will play video files from iTunes, and if Vista is worth the wait.

If you have a question, send it to me at mossberg@wsj.com, and I may select it to be answered here in Mossberg’s Mailbox.

I have an iPod which uses iTunes software on my Windows computer. With the iTunes software comes QuickTime. I do not want QuickTime to play video files. I wish to use Windows Media Player as the default player. Must I use QuickTime as a video player in order to use iTunes for music?

No. QuickTime is an Apple program that is required by iTunes, even on Windows computers. It can also be used on its own to play some video and audio files. But, if you set its preferences so it isn’t the default player for various types of video files, and you set Windows Media Player as the default, you should be able to use the latter, as in the past. There is one exception: If you purchase videos from Apple’s iTunes Music Store, you can only play them in either iTunes or QuickTime, not Windows Media Player.

Before we buy our daughter a laptop for school, should we wait until the new Microsoft operating system is released next year? If not, should we buy a laptop with a more powerful chip with the intention of upgrading once it is available?

It depends on when she needs the computer. If she can wait until January, when the new Windows Vista will be available preloaded on laptops, then wait. Vista should have significant advantages over Windows XP in the areas of security and user interface.

However, if she needs it now, you may be able to get a laptop that can be upgraded later to Vista. The trick is that Microsoft hasn’t yet published the specs for a laptop that can be upgraded to Vista. My best advice would be to buy the most powerful processor you can afford, a full gigabyte of memory, and a video system that is called “discrete,” rather than “integrated,” with as much dedicated video memory as possible.

I’ve been using the Dragon Naturally Speaking speech-recognition software on my Windows PC at work. Is there a comparable product for the Mac I use at home?

Yes. There are at least two speech-recognition programs for the Mac. One is IBM’s Via Voice (www.nuance.com/viavoice/osx/) and the other is called Mac Speech (www.macspeech.com/). I haven’t tested them, so I can’t say how they compare with Dragon on Windows, or which is best.

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about converting videos to play on a video iPod, opening multiple Web sites with a single click and power adaptors for using a laptop overseas.

If you have a question, send it to me at mossberg@wsj.com, and I may select it to be answered here in Mossberg’s Mailbox.

Q: Can I convert my home videos so they will play on a video iPod? If so, how?

Probably, though it depends on whether they are in one of the formats that can be easily converted, and it can be hard to tell in advance. You’ll need conversion software to do it. One option, for both Windows and Mac users, is to spend $30 to upgrade Apple’s free QuickTime media player to the pro version, which can convert numerous video file types to an iPod-compatible format.

Another option is to download one of many free conversion utilities that appeared on the Web after the video-capable iPod was released. For Windows users, there are numerous choices. One example is Free iPod Video Converter, at www.ipod-video-converter.org. If you use a Mac, one such program is iSquint, at www.isquint.org. I haven’t tested either.

I like to visit about 50 news sites every morning but don’t want an RSS feed only. I like to see the entire site. Is there a way to open all of them at the same time, without having to click on each bookmark one by one?

Certainly. All you need to do is switch to a tabbed Web browser, like Firefox or Opera for Windows or Mac; or Safari or Camino, for the Mac only. These browsers can open multiple Web sites, in the same window, marking each site with a tab bearing its name. And they allow users to open these multiple sites with a single click. Though each differs slightly, all have a command — usually called “Open in Tabs” — that will open a list or folder full of bookmarks with one click. For instance, every morning I open about 20 technology-related Web sites in Firefox or Safari with one click.

I would like to purchase a laptop computer in the U.S. but use it for extended periods in Europe. Is there anything I have to modify because of the difference in the electrical power supply?

Most laptops I have tested in recent years have power adaptors that can handle both U.S. and European electrical standards. Just make sure the one you choose is similarly equipped. The only thing you’d have to buy is a cheap plug adapter — not a transformer — to physically fit the plug into the sockets used in the European countries where the laptop will be used.

Write to Walter S. Mossberg at mossberg@wsj.com

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about finding people or companies mentioned in blogs, disabling the Caps Lock key and playing Windows Media Video files from the Web on a Mac.

If you have a question, send it to me at mossberg@wsj.com, and I may select it to be answered here in Mossberg’s Mailbox.

How can I tell if a person or company is mentioned in an online blog?

You can’t tell with 100% certainty. But there are some search engines that can give you a pretty good idea. These sites search blogs, or the syndicated feeds of blog headlines and article summaries called RSS feeds.

Google is testing a blog search site, at blogsearch.google.com. You might also try Feedster, at feedster.com; and Bloglines, at bloglines.com. If you want to be automatically alerted when a person or company pops up in a blog, you can use a so-called news reader, which scours the feeds of blogs and other sites.

Some allow you to set up a custom feed, based on search terms of your choice. When you create such a feed, the news reader software will periodically list headlines of blog entries that match your search terms.

Is there a way to disable the Caps Lock key on a Windows PC?

There are a number of small programs and tweaking methods for disabling the Caps Lock key, so you don’t hit it accidentally while typing. I have tried only one, called CapsUnlock, that worked well in a brief test I conducted. It can be downloaded at www.brainsystems.com/capsunlock. CapsUnlock is a tiny program that runs in the background. When it is running, tapping the Caps Lock key has no effect. You can override this effect by holding down the Shift key while tapping Caps Lock. The program also disables the Insert key, another annoying accident waiting to happen.

Is there any program that will play Windows Media Video (.wmv) files from the Web on a Mac?

There are three major programs for playing video and audio files on the Internet — Microsoft’s Windows Media Player, RealNetworks’ RealPlayer, and Apple’s QuickTime Player. Because Apple makes the Macintosh, it bundles QuickTime on each Mac, but not the others. However, Mac owners can have all three, free of charge. And so can Windows users.

Microsoft has created a free, simple version of Windows Media Player for the Macintosh. It will play back Windows Media files, both video and audio. You can download it free at www.microsoft.com/mac/. Just click on “Other Products” in the list at the left, and scroll down until you see the listing for Windows Media Player. Once it’s installed, you can play Windows Media clips from Web sites, or from a disk, or from email attachments.

Similarly, RealNetworks makes a free version of RealPlayer for the Mac. Go to www.real.com/mac/, and click on the button at the top right that says “RealPlayer — Free.”

If you are a Windows user, you already have Windows Media Player. You can download QuickTime at www.apple.com/quicktime/. You can download RealPlayer at www.real.com — just be sure to find the small link for the free version of the player, unless you want a paid subscription to Real’s content services.

Because of the volume of e-mail I receive, I can’t routinely answer individual questions by e-mail, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

Write to Walter S. Mossberg at mossberg@wsj.com

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about converting video clips for use with the new iPod, different DVD formats and finding the FolderShare program for a Mac.

If you have a question, send it to me at recommended a program called FolderShare, which can automatically synchronize files among multiple Windows and Macintosh computers. Now the company has been bought by Microsoft, and the Mac version of the software has disappeared from its Web site. Do you know if they are abandoning the Mac?

FolderShare removed its Macintosh version for a couple of weeks to rework it, but now has restored it. Not only that, but Microsoft has converted FolderShare to a free, instead of a paid, service. However, one advanced feature has been removed, and the number of files you can synchronize has been lowered, though at 100,000 files, it’s still a lot. It is available, for both Windows and Mac users, at www.foldershare.com. I should note that, in addition to working in mixed groups of Windows and Mac computers, FolderShare will work in groups with only Windows, or only Macintosh, machines. I use it daily, and find that it works well.

* * *

Because of the volume of e-mail I receive, I can’t routinely answer individual questions by e-mail, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

Write to Walter S. Mossberg at mossberg@wsj.com