Put in the wi dows 7 disk boot from that, this method will erase everything, but restore the computer to how it first was when bought.
With the windows 7 disk in, click install, bottom left will be a repair option, click the repair option
You will be at a screen with several choices, you can choose to check for startup errors or what I reccomened is first
If you want to try to save the data, open the command prompt,
type chkdsk /f /r c:
Or chkdsk /r c:
If you want the drive wiped Clean, open the command prompt
Type diskpart
Once it's loaded
Type list disk
Type select disk 0(or 1 depending on which drive has your os)
Type clean [this will delete everything warning]
Type create partition primary
Type select part 1 (or 0 if 1 does not work)
Type active
Type format fs=ntfs label=local disk quick
After formatting is done
Type assign letter c
Now just reboot your computer, install win 7 from your disk and it's brand new
Please let me know the results after yur finished.