With Windows 7 USB/DVD Download tool you can make a bootable USB with a Windows 7 ISO image.
Download and instructions: http://www.microsoftstore.com/.....vd_dwnTool
To get an original, official Windows 7 with SP1 ISO image: http://forums.mydigitallife.in.....post470600
Once you have this, insert your bootable Windows 7 Install USB and boot from it. Select "Repair your computer". Click "next" and open a command prompt. Then do this:
Change directory to w:\boot, where W: is your Windows 7 Install USB:
cd /d w:\
Run BOOTSECT.EXE /NT60 C: , where C: is your System partition.
Finally, make sure your C: partition is active:
In Diskpart, type "list disks" or "list disk", can't remember which one is right.
Type "select disk 0" where 0 represents the number of your hard drive.
Type "list partitions" or "list partition", can't remember which one is right.
Type "select partition 1" where 1 represents the partition where you have Windows installed.
Type "exit", then "exit" again and restart to see if it works now.