you can simply repair your MBR of windows
- Insert your DVD of Windows 7
- WHile Booting, click on Repair your computer
- Now in Command prompt
- Type the following Command
Bootrec /FixMbr // If you have Damaged MBR
Bootrec /Fixboot // If you’r MBR is having problem or Missing.
Bootrec /Rebuild //If you’re MBR is Compressed or unable to repair
You can find the detailed process here at How to Fix/repair/Rebuild MBR in Windows 7/8