Boot Manager problems

Alright, so I've gotten myself in quite the pickle!

A buddy of mine's hard drive crashed, so I was going to lend him 250GB storage backup drive. It just has a copy of my music, movies, games etc, just in case my other storage drive died, it wasn't in RAID or anything just a back up.

Apparently it had the boot manager on it, since at one time it was the primary hard drive when I was dual booting the beta for win 7 and Vista. So when I went to boot up my computer and alas no boot manager found.

So I used my Win 72 pro 32-bit disk, I have 64-bit installed on my computer but that disk is currently in storage, that I had won in a contest from school I had no valid key but still I figured it would find the OS and voila repaired problem solved, no dice. Didn't see the OS on my main 750GB, so I assumed that if I installed the OS it would recreate the Boot Manager and see the other OS, then I could just go in and delete it off that hard drive and just always pick the "real" OS I was using.

Didn't work.

THEN I tried installing a third party Boot Loader (GAG bootloader) and it didn't see it either just the newly installed non-configured 32-bit i have no key for.

So, I call up my body who just finished reinstalling vista on the borrowed drive and ask him if when he reboots he sees options for other OS'es he says he does. I go and get my hard drive back.

I put it back in, uninstall GAG (which doesn't see the other OS still) and it still wants to boot the 32-bit 7, I unplug that hard drive all together thinking maybe it will see the other drive now when searching for a boot loader and no dice still wants to load the new 32-bit.

Long story short, I need help. I have about 450gigs of stuff on the main drive that vast majority of which I would prefer not to lose.

I can get my copy of the original disk 64-bit install disk tomorrow and hopefully the repair function should work on that if it doesn't will I have to reinstall? I'm not sure if I can still get access to the key I used (though I might). Since i got it through MSDN-AA and I no longer have access since I am no longer enrolled in any computer related courses.

Please help

If you need to save 450 gig of info(wow that's a lot). I would get another HD just to reinstall windows. Then install that HD and copy the data.
PS rebuilding the MBR may work and if not should not delete your data.
MBR - Restore Windows 7 Master Boot Record

I'm going to try restoring the MBC with my 64 disc since the 32-bit disc doesn't see the 64-bit version.

If that doesn't work, I will probably boot a live CD of Linux and move what I need moved onto my other 250GB hard drives and *hopefully* track down my CD-key and reinstall windows.

Unless there are other suggestions.

A live cd should work. Not sure how you have the 250 HD connected if by usb connected it first before you boot from the cd.

Hazaah I fixed it.

What I ended up doing, after other tinkerings, was delete the new boot manager and was able to replace it with the old one using Ubuntu which I booted from a disc.