|Post exact system spec's.|
Did your system come with Windows 7?
If upgraded, what was your original OS?
Have you been having other problems prior to this one? What?
If your system came with W7 pre-installed, run Memtest from a bootable CD to see if you have memory problems?
If your system came with W7 pre-installed, try a repair from recovery partition.
Answer these questions and tell us ALL you have tried so far so we can get to the root of the problem.
You have to be a little bit crazy to keep you from going insane.