First make sure the Windows 7 HD is set as first HD to boot in BIOS setup.
If it still fails to boot, then mark Active
the Windows 7 partition or it's System reserved boot partition (preferred): Mark Partition Active.
Then run Startup Repair - Run 3 Separate Times
until Windows 7 boots on its own and holds the System Active flags.
Unplug all other HD's while you do this. Make sure Windows 7 HD remains set first to boot in BIOS setup going forward.
If this fails you can post back a camera snap of your drive map and listings after booting free Partition Wizard
Or you can remove all but the target HD for reinstall, boot the Windows 7 DVD to Clean Reinstall - Factory OEM Windows 7
- the steps are the same for retail and include the latest official installer with SP1 and how to rescue your files.