Have you tried running SFC from a Command Prompt booted from the Windows 7 install DVD? Tutorial by Brink here: SFC /SCANNOW : Run in Command Prompt at Boot
If you do not have a Windows 7 installation DVD, you can download a legal copy with SP1 integrated from here: Official Windows 7 SP1 ISO from Digital River
Make sure you get the same version you have, Home Premium, Pro or Ultimate and 32 or 64 bit. Note that Basic or Starter is not available.
I recommend using ImgBurn
at 4X speed (or the slowest available) to create the DVD from the downloaded .iso file.
Just had another thought. You should run chkdsk /r
from a Command Prompt booted from the Windows 7 install DVD first in case there are any file system errors present. Then run sfc as indicated in the tutorial.