Devlin Carnet,
If you want to get rid of the problem, you could use the WinXP CD to do a fresh install of WinXP on top of itself. As long as you tell it during the install to keep the current file system intact you will only lose any data you had in the Windows Directory.
If you are going to go this route, just make sure you have all the drivers for your hardware downloaded (including SP2) before starting the fresh install.
Take Care,
Richard
P.S. I just thought of one more idea, try creating a new Administrator Account and delete your current account. Then if you still get the serious error, right click on your Hard Drive and go to Properties >> Tools >> Error Checking >> Check Now Button. Put a check mark in both options and hit the Start Button. The computer will want you to reboot in order to run the check. Reboot and just let it run.