How to speed up your computer

I'm running into a problem. Whenever I try to check for disk errors, it stops at Phase 2 and says "Windows was unable to complete the disk check". I followed the instructions on that link.

:f6:

For automatically fixing file system errors runs Chkdsk by using the /f parameter. All files must be closed for this program to run. If the drive is currently in use, a message asks if you want to reschedule the disk checking for the next time you restart your computer.