What attempted repairs have you tried? Did you do a system restore?
If you already tried system restore, I would suggest going through the steps for
Troubleshooting Windows 7 Failure to Boot and closely following that guide.
For the step to use
SFC /SCANNOW : Run in Command Prompt at Boot to check your system for errors, make sure you select the correct drive letter as it may not be C:. It could be D:, E:, F:, or even G:. It will not be X: To determine which drive letter contains Windows, find the drive with the Windows directory using the following command prompt commands:
C:
dir
D:
dir
E:
dir
F:
dir
G:
dir
etc. until you see Windows listed as a directory.