Without a doubt, the SP2 nightmare that's gotten the most press is this: After installing the update, some of the software that once worked fine on your PC simply doesn't function. Microsoft explains the problem by saying that SP2 is no normal service pack (just a collection of previous bug fixes) but is more like a top-to-bottom upgrade of XP. Analysts generally agree.

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Actually, while the problem is bigger than Microsoft admits, it's not all doom and gloom. Microsoft Office still works fine after the update, and so does Intuit Quicken. In fact, probably 99 percent of software that runs on XP runs fine on XP SP2. Still, statistics won't make you feel any better when you fire up Ye Faithful Application and it chokes.

1. Check out Microsoft's list of "Programs that are known to experience a loss of functionality."

The most common SP2 problem that plagues applications is Windows Firewall wanting to block access to the Internet. The simplest way to fix this? Run the app and click Unblock.

• Steer your browser to this Microsoft-authored list of 37 (the count when we wrote this) programs that have issues with SP2. They range from the puny--AOL's toolbar--to the big deal, such as WordPerfect Office.
• If the app that's giving you fits is on the list, check with the program's maker. It may have a issued a downloadable fix by now.
• If not--possible, since Microsoft's list is by no means comprehensive--head to the vendor's Web site and do a quick search for "SP2." That's how we discovered how SurfSaver, one of our most important browsing tools, could be resurrected after installing SP2.

2. Unblock Windows Firewall.
After installing SP2, some software may not run properly because Windows Firewall is now blocking one or more ports that the application or game needs to communicate with another computer or server.

Here's the easiest way to unblock an app:

• Run the program.
• When the dialog box alert appears, click Unblock this program.
• Click OK.

If you disabled Windows Firewall because you're using another firewall, you can safely skip this step; most apps will work as before. For those that don't--typically, the SP2 updates to Microsoft titles such as Windows Messenger and Internet Explorer--enable them using your firewall's own unblocking tactics.

3. Browse Microsoft's second list of bamboozled apps: "Some programs seem to stop working."
Some programs, including a few of Microsoft's own, need to have ports opened manually to work behind the Windows Firewall. That's a hassle, but at least there's help on the Web.

• Head to the next Microsoft list, which posts 49 applications and games temporarily stymied by Windows Firewall.
• Skim the list. If the app or game you're having trouble with is on the list, follow the directions on that page to open the specified ports.