And in the United States, the country that invented the Internet? It’s 5.1.

This according to a new study by the Communications Workers of America, which found that broadband speeds in the States are among the slowest of the 29 countries it surveyed. “Between 2007 and 2009, the average download speed in the United States has increased by only 1.6 megabits per second (mbps), from 3.5 mbps in 2007 to 5.1 mbps in 2009,” the CWA explains in its report. “At this rate, it will take the United States 15 years to catch up with current Internet speeds in South Korea, the country with the fastest average Internet connections.”

And no wonder: 18 percent of Internet connections in the States that the CWA surveyed revealed download speeds slower than 768 kilobits per second, which doesn’t even qualify as basic broadband according to the Federal Communications Commission’s definition.

That may soon change, now that the country has adopted the American Recovery and Reinvestment Act, which includes a provision for a national broadband plan by spring of 2010 and grants of $7.2 billion to bring high-speed Internet to the hinterlands. But it will be slow going. It’s a long way from 5.1 mbps to 20.4.

I’ve never stepped foot in the state, though I have peered out at Wilmington from the window of an Amtrak car. But Akamai (AKAM) tells me I’ve get better odds of getting a high-speed connection there than anywhere else in the U.S.: 62 percent of the state’s Internet connections run at more than five megabits per second, and the state has the highest average speed in the country. The numbers come via the content delivery network’s quarterly “State of the Internet” report, out today.

According to Akamai, 5Mbps fits its definition of “high broadband,” and it’s the speed the company says you’ll need to have in order to watch a DVD-quality movie on your PC, though a mere 2Mbps will let you watch a TV show.

Of course, if you’re really want a good broadband connection, you’re better off living outside of the U.S. altogether. America ranks 18th in the world in average connection speed, and lags behind 11 other countries when it comes to “high broadband” connections. And if you’re reading this in Japan or South Korea, chances are this page got to your screen very, very quickly.

You can see the full report for yourself here. More interested in babies on rollerskates? OK. I can accommodate that need, too:

Should I install Microsoft’s “SP3″ upgrade to Windows XP? I hear opinions on both sides.

In general, I recommend this upgrade, officially called Service Pack 3, because it beefs up security, and that helps not only you, but all Windows users, to avoid the spread of malicious software. If your PC is more secure, it is less likely to be used as a source from which other PCs can be infected.

I have upgraded a couple of XP PCs to SP3 without any downside. However, like you, I have also heard from some users that the upgrade caused them problems.

As with any major operating-system upgrade, either outcome can occur, depending upon your computer’s particular configuration and condition. So, if you’re on the fence, consider your level of concern about security.

How do cellular data cards compare with fast cable modems in terms of Internet speed? Are these cards more secure than Wi-Fi?

In my experience, using and testing cellular data cards on various laptops, they typically deliver, in real day-to-day use, somewhere between 300 kilobits per second and 1.5 megabits per second. By contrast, a fast cable Internet service can actually deliver up to 16 mbps. So cable is much faster.

Your security question is much more complicated. Wi-Fi security can range from very poor to quite good. It depends on where and how you use Wi-Fi, how you or others have set up the wireless network, and how you have configured your own computer.

Accessing the Internet over a cellular network is a more controlled process, because the cellphone-network operator manages the transmission, and in most cases supplies and configures the software on your computer. So, it is likely to be safer than the worst Wi-Fi setups. But I would never suggest that cellular data card transmissions are invulnerable to hackers or criminals.

What’s the difference between file-based backup and image-based backup software? Why would I choose one over the other?

Image-based backup software copies an image of your entire hard-disk, including all the programs, settings and obscure files that you never see. While it can be used to recover individual files, in some cases, it is mainly designed to allow you to restore your entire hard disk in the event that you lose it all.

File-based backup software, which is more common among consumers, is typically designed to preserve a copy of only your personal data, the material you can’t re-purchase or re-install if your hard disk dies.

That includes word-processing files, spreadsheets, presentations, emails, contacts, calendar items, photos and other items you created. It also is often used to back up music and video files that would be time-consuming, or very expensive, to re-acquire. And in some cases, it can preserve settings and preferences, such as Web bookmarks.

Both types of backup generally begin with a time-consuming initial session, followed by shorter sessions to update the backup with incremental changes.

Many people choose file-based backup because it occupies less space, and is generally quicker and also less expensive. Image-based backup is for folks who are willing to spend the added money and time to be sure they can restore their whole computer, or clone its contents completely to another machine.

• You can find Mossberg’s Mailbox, and my other columns, online free of charge at the new All Things Digital Web site, http://walt.allthingsd.com.

With U.S. broadband speeds lagging far behind European and Asian countries, Comcast is finally doing its part to bring the country’s lousy broadband Internet services into parity with those of other industrialized nations. You know, like Iceland. Or South Korea.

Comcast (CMCSA) plans to aggressively deploy its next-generation wideband service to 10 million homes by the end of the year, the company said Wednesday. Based on the ultrafast Data Over Cable Service Interface Specification (DOCSIS), the service should provide download speeds far in excess of those currently offered by the company. It’s to be offered in two tiers. The fastest, Extreme 50, will provide up to 50 megabits per second downstream and up to 10Mbps of upstream speed. Price: $139.95/month. Ultra will get you up to 22Mbps downstream and up to 5Mbps of upstream for $62.95/month.

And what about the 150Mbps service Comcast CEO Brian Roberts demonstrated at the Cable Show last year? The one fast enough to download the entire “Encyclopedia Britannica” and “Merriam-Webster Visual Dictionary” in less than four minutes? Still a ways off, apparently.

PREVIOUSLY:

• The Median U.S. Broadband Speed? Finland’s Divided by 10

With U.S. broadband speeds lagging far behind European and Asian countries, Comcast is finally doing its part to bring the country’s lousy broadband Internet services into parity with those of other industrialized nations. You know, like Iceland. Or South Korea.

Comcast (CMCSA) plans to aggressively deploy its next-generation wideband service to 10 million homes by the end of the year, the company said Wednesday. Based on the ultrafast Data Over Cable Service Interface Specification (DOCSIS), the service should provide download speeds far in excess of those currently offered by the company. It’s to be offered in two tiers. The fastest, Extreme 50, will provide up to 50 megabits per second downstream and up to 10Mbps of upstream speed. Price: $139.95/month. Ultra will get you up to 22Mbps downstream and up to 5Mbps of upstream for $62.95/month.

And what about the 150Mbps service Comcast CEO Brian Roberts demonstrated at the Cable Show last year? The one fast enough to download the entire “Encyclopedia Britannica” and “Merriam-Webster Visual Dictionary” in less than four minutes? Still a ways off, apparently.

PREVIOUSLY:

• The Median U.S. Broadband Speed? Finland’s Divided by 10