Unplug all other HD's. Boot the Windows 7 DVD Repair console or Repair CD, press Shift F10 to open Command Box, type:
DISKPART
LIST DISK
SELECT DISK 0 (confirm this is Windows 7 HD #)
LIST PARTITION
SELECT PARTITION 1 (confirm this is Windows 7 partition #)
ACTIVE
EXIT
Now boot back into Repair console, click through to Recovery Tools list to run Startup Repair up to 3 separate times with reboots to write the MBR to Windows 7.
To copy out your files if it won't Repair:
Copy & Paste - in Windows Recovery Console