When you plugged back in the other HD and set it first to boot, then Windows 7 started up again, correct?
I'm assuming this is when you tried moving the boot files to C. Does C now hold the System flag? Check using free Partition Wizard
If not unplug other HD, boot PW CD to mark C Active, then click on HD # to highlight it, from Disk tab select Rebuild MBR, Apply. See if Windows 7 will start.
If not run Startup Repair 3 separate times with reboots again, until Windows 7 starts.