Stick your Windows 7 dvd into drive and reboot computer from cd drive
When it brings up the options click "Repair and Restart". Done!
I originally ran XP and then I bought a 2nd HDD and installed Windows 7 on it and it automatically set up a dual boot. I replaced the XP HDD with a new one and installed Window8 on it and I expected to again have a dual boot setup. Nope.
I took nhorton79's suggestion and booted up the Windows 7 CD and ran repair. It found the Windows 7. The first time I booted into Windows 7 CHKDSK started and it went through both drives. I was in a panic that I had destroyed my Windows 7 but it all came out OK.
The dual boot is slower than the one I had previously but I am a happy camper now.