Generally speaking, Service Pack 2 makes it harder for other computers to "talk" to your computer, especially over the Internet. Previously, Windows computers were relatively easy to contact and "talk to" over the Internet, and it was exactly this feature that helped contribute to the number of compromised Windows computers on the Internet. Sadly, many features that were designed with ease of use in mind have been turned into security "holes" by certain members of the computing community.
And because most of the new SP2 security features work to close these security holes, you might experience difficulty if you're using a machine that needs to communicate with other computers over the Internet. Don't misunderstand: if you use your XP system for browsing the Internet and sending email, you shouldn't have any problems. You might experience difficulty, however, if you're using your XP machine in any of the following ways:
Most of the problems with these services are caused by the default settings with Windows Firewall, which can be configured to allow necessary traffic for the desired applications. The most popular Microsoft Knowledge Base article for Service Pack 2 is called "Some programs seem to stop working after you install Windows XP Service Pack 2," and it can be found at http://support.microsoft.com/kb/842242.
If you still find that SP2 causes too many problems with existing software, you can use Add or Remove Programs to remove SP2 and restore your computer to its previous state. It's no trouble at all. Here's what you do:
If you run into trouble after removing SP2 (or after installation of any program, for that matter), you can restore Windows to a previous state. To do so, use the System Restore Wizard by clicking on Start | All Programs | Accessories | System Tools | System Restore. System Restore will be covered in Chapter 13.