If you have a backup made by Windows utility or a restore point, you can boot with the original Win7 DVD and click "repair" after the first screen with language choice.
If you have working the keyboard under BIOS, normally you have it in WinRE too. WinRE is the small OS loaded with a repair USB key or DVD, or by the original DVD with complete OS onboard.
After you go to advanced utilities and you can chose to restore from a restore point or from a Windows backup.
It has to work, in theory