You know, You don't have to back everything up if you're just going to reinstall Windows.
There is an option you choose prior to the install, something along the lines of "Repair an Existing Copy" or something like that. It will repair the Windows directory itself, and it will leave everything else alone.
Now if you want to FORMAT, then you need to back up important files.
Also, Try re-seating your ram modules. See if that does anything.