Use the ultimate configuration tool (Professional Edition only)

One of the most full featured Windows XP configuration tools available is hidden right there in your system, but most people don't even know it exists. It's called the Local Group Policy Editor, or gpedit for short. To invoke this editor, select Start and then Run, then type the following:

gpedit.msc

After you hit ENTER, you'll be greeted by gpedit, which lets you modify virtually every feature in Windows XP without having to resort to regedit. Dig around and enjoy!

GPEDIT: It's your best friend for XP configuration.

Use the Windows Sound Scheme
Contributed by Keith Furman
Windows XP ships with a really nice new sound scheme, but it's not loaded by default for some reason. So once you've installed Windows XP, one of the first things you should do is get that new sound scheme loaded.

To do so, open up Control Panel and navigate to Sounds, Speech, and Audio Devices. Then, choose the task titled Change the sound scheme. In the dialog that appears, choose Windows Default for the sound scheme. Windows will ask you whether you want to save the previous scheme, which is usually a brain-dead questions, since no scheme was previously loaded. So choose No, and then click OK to exit the dialog.

Rip high-quality MP3s in Media Player for Windows XP (MPXP)
Contributed by Mark Elder, updated by Paul Thurrott
The relationship between Media Player for Windows XP (MPXP) and the MP3 audio format is widely misunderstood. Basically, MPXP is able to playback MP3 files out of the box, but encoding (or "ripping") CD audio into MP3 format will require an MP3 plug-in. During the Windows XP beta, Microsoft supplied a sample MP3 plug-in for testing purposes, but it was limited to 56 Kbps rips, which is pretty useless, leading some to report that Microsoft was purposefully hobbling MP3 to make its Windows Media Audio (WMA) format look better. This is not the case.

To enable MP3 encoding in Windows XP, you'll need to to purchase one of three MP3 Creation Add-on packs for Windows XP. For more information, please visit the Microsoft Web site.