There are a few things you can do to help keep your computer running smoothly, which are built into Windows. The first is "Disk Defragmenter" which I would suggest you run weekly. To find it (in Windows XP) select "Start" then "all programs" "Accessories" "System Tools" "Disk Defragmenter" Select your primary hard disk first (Your "C" drive) and click on the defragment button. Once completed, select any other hard drives you may have, and defragment those as well. If you haven't done this recently, it may take some time so please be patient. An Excellent alternative to the windows disk defragmenter is "Diskeeper Lite" which can be downloaded HERE this defragmenter is slightly faster than the windows one.
When using "Internet Explorer" It is a good idea to clear out all the clutter it collects. With Internet Explorer open click "Tools" "Internet Options" then delete Cookies, Files, & History (Including deleting offline content) this should help in giving you a faster internet experience.