You will need to isolate the fault either software or hardware fault.
First get a spare hard drive and install Windows, if that works ok then you know hardware is ok.
If software fault, only way to clean up your Windows, defrag, disk cleanup, tuneup, Windows Registry cleanup, if all doesnt work, only way to reinstall Windows
http://www.pcglow.co.uk
Hope that helps
Gareth Gunn, November 2007