Try booting from a Linux live CD.
If you can, copy your files to some external drive.
If you have any problem booting from the live CD, you may have some memory problem. Run the memory test that should be accessible from the startup menu of the CD.
If it shows any error, even only one, you realy need to replace any affected memory stick. Faulty memory CAUSES all sort of impossible to solve and elusive problems and may make your installation look corrupted.
It's possible that your Windows installation have been corrupted.
If you have Windows Vista, 7 or 8:
Boot from the install DVD and sellect the "Update" option.
The update operation will preserve any user data and all installed programms. You'll need to reapply all updates to Windows.
If you have Windows XP, you don't have that option. You need to reinstall Windows. This will probably suppress your data and you need to back them up BEFORE you start the reinstall operation.
You may restore back to factory settings, but it will erease any data, remove any installed programms and bring back any bundled programms that you have removed.
Electro, December 2012
