There are several things you can do to clean up and improve the performance of your Windows XP Computer.  Here are some basic items

1)  Cleanup - Click on Start, Click on Programs, Click on Accessories, Click on System Tools, Click on Disk Cleanup and select your hard drive - usually C:\

This utility program will run for awhile and will find those items that you can delete on your system.  Temporary files, recycle bin etc.

After you clean up your computer go to the next step

2)  Defragment your hard drive - Windows has again a simple tool -- there are other ones out there that you can pay for like DiskKeeper but use this one for a start.

Click on Start, Click on Programs, Click on Accessories, Click on System Tools, Click on Defragment.

Two simple steps that can improve the performance of your computer.

Remember, always backup your important files and keep your virus definition files current to avoid problems in the future. 

Make it a profitable day!