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 deleting groups of emails on a Treo, eliminating unnecessary background programs and sending files from a Mac to a Windows PC.

How do I delete groups of email messages quickly on the Treo smartphone?

It depends on which Treo model you are using and which email program you are using. If it’s a Windows-based Treo, like the Treo 700w or 700wx, you can’t delete large groups of messages very quickly in the built-in email program. You have to manually select large groups of messages and then use the delete function. If it’s a Treo model that uses the Palm operating system, like the Treo 700p or the 650, it is usually possible to do this automatically with a few keystrokes, though the method varies depending on which email program you are using.

If you are using my favorite Treo email program, SnapperMail, on a Palm-based Treo, and you want to delete all or many of the messages in a mailbox, such as your inbox, you can do so with one hand and as few as three keystrokes. This “Purge” command allows you to delete all the messages, or only messages older than various periods of time you can set. You don’t have to use the stylus, or manually select any messages, or use two hands. You just press the menu button, the “T” key, and the center button on the navigation pad.

When I open the Windows Task Manager, I note that there are anywhere from 52 to 57 “processes” operating on my PC. I am sure this is slowing things down. However, the names of the programs are virtually impossible for a nontechie to understand so I don’t want to eliminate any of them for fear of causing major damage to the operating system. Short of calling a service technician, is there a way for me to find out which processes can be safely shutdown and/or eliminated?

This is one of the major banes of using Windows — every program and even some Web sites think it’s OK to install and run in the background all sorts of little, and not-so-little programs, which create the “processes” you are seeing. Some of them may even be spyware and adware. And, yes, they do slow down your computer.

Unfortunately, I don’t know of any quick, easy way a mainstream, nontechie user can tell which ones can be safely shut down. There are programs like Startup Cop that help you decide which unseen programs you should allow to launch when your computer starts, but they don’t necessarily cover stuff that launches after start-up. And there are Web sites, like processlibrary.com and answersthatwork.com, which let you look up a process to see what it does, but that is a laborious process. The latter Web site offers a $29 program called the Ultimate Troubleshooter for managing all these processes, but it’s pretty intimidating for a nontechie.

Antivirus and antispyware programs can shut down some malicious background processes, or stop them from loading in the first place. But many of the resource-draining “processes” you are finding may be from “legitimate” programs on your PC that simply want to hog the computer.

If I switch from Windows to a Macintosh, will my colleagues be able to read any Mac files I send them?

There is no such thing as a “Mac file.” The Macintosh today can create and read all the major standard types of files that Windows PCs use. For instance, photos in the common JPG format; music files in the common MP3 format; Adobe PDF files; text files; and many other types of files can simply be moved between Windows and Mac computers with no conversion necessary. Microsoft Office files, like Word, Excel and PowerPoint documents, can also be shared between the two platforms, without conversion, if you have the Office program suite on both ends. The Mac’s built-in email program, Apple Mail, even has a setting for sending “Windows Friendly” attachments.

There are some specific programs on both platforms that can create proprietary file types not easily opened, or opened at all, on the other platform. Most annoyingly, the Windows and Mac versions of Quicken don’t share a common file format. But now that the new Macs can also run Windows, you can always launch Windows on your Mac in a pinch to run a program that can handle some Windows-only file type.

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Because of the volume of email I receive, I can’t routinely answer individual questions by email, 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

But many corporate information-technology departments have refused to buy the phone. Why? Because the Treo is powered by the Palm operating system and not by software from Microsoft, the only company whose software is supported by many IT departments.

So Palm this week introduced a Treo model that uses the latest version of Microsoft’s Windows Mobile software (formerly known as Pocket PC). On the outside, the new Treo 700w looks very much like the current Palm-based model, the Treo 650, which will remain on sale and will continue to be developed on a parallel track. On the inside, though, the new Treo’s key software functions — phone, email, Web, multimedia — are all different.

I have been testing the Treo 700w, which will be sold by Verizon Wireless, to see how it stacks up against the Treo 650, the phone I carry every day.

My verdict: Despite some nice new features, the Windows Mobile software is still inferior to the Palm software for one-handed use on the go. Its crucial email and phone functions are also weaker. And there’s a serious bug in its email software that affects individuals, though not corporate users. So the Treo 700w is neither as easy to use nor as powerful as the Treo 650. In addition, the screen on the 700w offers significantly lower resolution than the screen on the 650, and the new model costs twice as much — $400 versus $200.

For individual users, the main advantage of the new Treo 700w is that it is the first Treo to work on Verizon’s high-speed EV-DO network. That network delivers data speeds that rival those of home DSL lines. But the speed advantage will be short-lived, because I expect to see a Palm-based Treo in coming months that can also use the EV-DO network.

At first glance, the phones look nearly identical, though the new 700w is a bit more rounded. The key dimensions are all the same, but the color scheme is a bit different and the 700w has a slightly better keyboard. The individual keys are squarer, with a bit more room between them.

The built-in camera on the new model is much better than the primitive one on the 650. It can shoot at a resolution of 1.3 megapixels, up from just a third of a megapixel for the older camera. In my tests, the 700w’s pictures were much better. But the resolution of the screen on the 700w, a vastly more important component, has changed for the worse. Although it is about the same physical size as the 650 screen, it has a resolution of only 240 by 240, 44% lower than the 320-by-320 resolution on the Treo 650 screen.

There are some offsetting pluses. In my tests, downloading Web pages on the Treo 700w was wicked fast for a hand-held, typically hovering between 500 and 800 kilobits per second, roughly 10 times as fast as on the Treo 650. Also, the new model has more than twice as much usable memory, and slightly better claimed battery life.

Palm has also added some nice features to the Windows Mobile software. The Today page, which summarizes information like appointments and unread email, has been vastly beefed up. It now includes a box for looking up phone numbers and one for doing a Google search.

In addition, you can quickly initiate a phone call from the Today screen in a number of ways: You can start typing a number or a name from your contacts list, and that contact will pop up. You can use a previously assigned speed-dial letter or number. Or you can set up a scrolling bar containing photos of your frequent contacts and then tap on the relevant picture.

Palm has added other goodies. You can choose to respond to an incoming call with a text message, which is great if you’re in a meeting. And when listening to voice mail, you can use VCR-like icons to navigate among messages.

But lots of tasks on the Treo 700w require extra steps. On the 650, one click of a button takes you to email. On the 700w, two button presses are necessary. On the 650, the leading email programs allow you to delete a message by pressing one key. On the 700w, you have to press a key, view a menu and then press a second key.

And the email program lacks many of the advanced features of VersaMail or SnapperMail on the Palm-based Treo. For instance, there’s no simple way to delete — or to mark as read — large groups of messages.

When you’re on a phone call on a Palm-based Treo, you can turn on the speaker phone or mute the microphone by tapping large icons with your thumb. On the Windows-based Treo, you have to open a menu and then select these functions.

And then there’s that email bug. If you’re using a so-called POP email account, like the ones offered to consumers by EarthLink and many others, the Treo 700w will disconnect from the network after it checks for new email. This means that when the 700w next checks for email — or when you next try to get on the Net — you’ll have to wait for it to dial into the network again, which is annoying. Microsoft is working on a fix, but it will take months to deploy the patch to users.

The Treo 700w will appeal to some Windows Mobile fans, and to some corporate IT staffs. But for everyone else, I advise sticking with the Palm-based Treos.

• Email me at mossberg@wsj.com.