Not one of the experts, but I've learned a few things, and your topic caught my eye. If your goal is to basically de-clutter your computer safely and get it to run faster, there are other things you can do which are not only safe but are recommended you do on a routine basis to take care of your computer. Perhaps you don't know about them. They came with your Windows XP.
1. Run Disk Defragmenter. It shoves fragmented files together into one volume so that they aren't scattered everywhere in your computer's memory and your computer can access them easier/faster. It'll make working on your XP much more efficient. It doesn't delete anything.
To get to Disk Defragmenter, click Start, go to All Programs, go to Accessories, go to System Tools, and then click Disk Defragmenter.
2. Run Disk Cleanup. Unlike the defragmenter, this will delete stuff. It'll go through and delete temporary files, programs that are unnecessary, and your Internet cache files. You can tell it to delete what you want, and you don't have to delete everything if you don't want. However, deleting some of the Internet files may cause you to lose your Internet history or saved passwords, just as a warning.
To get to Disk Cleanup, click Start, go to All Programs, go to Accessories, go to System Tools, and then click Disk Cleanup.
Both of these will take time to run, sometimes upwards an hour, depending on your speed and how much stuff it has to clean up the first time around.
Simple things which helped me get my XP to run faster:
1. Keep your Recycle Bin empty. You'd be amazed at how quickly that bin gets full.
2. Go through your programs and see if there's anything you can do without. If you're feeling adventurous, replace some of the bigger programs with something else that will do the same job and take up less space. Check out this fantastic list assembled by BleepingComputer here
3. The fancier the graphics, the slower you move, especially if you're using tons of fading effects. I went through my computer's display properties and changed the traditional XP look to something more basic, a classic Windows theme. I personally don't mind it, and you can play with the colors if you want. To change it go to your desktop, right-click and go to Properties, then click the Appearance tab. On the Windows and Buttons drop-down menu, click on Windows Classic style. Then you can play around with the colors and effects as you like.
4. Buy more RAM, it's really cheap now!
If anyone else more knowledgeable than myself thinks any of this is a bad idea/wrong, please tell! Also, what is the general consensus here about CCleaner? Also bad?