Windows won't boot

[baseballer10p]

I was playing Fallout 3, and it froze on me. Nothing would work, I couldn't bring the task manager up or anything. So I switched off the computer, and when I go to turn it back on again, it won't boot into Windows. I get a message that says that there may be something wrong with a Windows startup file and asks me to insert my OS disc. I'm running Windows 7 RC 64-bit, so I pop it in, and restart.

Now it gives me the same error, and it won't boot from the DVD to repair. So I put in an Ubuntu disc I have lying around, and that won't boot either. Luckily, I got a new 750GB hard drive this summer, and I still have my old 120GB with Windows 7 RC 64-bit loaded on it. However, there is a lot less capacity, and there are a ton of new files on my 750GB drive. I switch the hard drives, with the Ubuntu disc still in, and that booted up fine. Instead of running the live CD version, I just booted into Windows 7.

So, I can't boot from either the hard drive or the DVD drive when I use my 750GB hard drive, but I can boot from both the hard drive and the DVD drive when I use my old 120GB hard drive. Can you help me figure out what the problem is so I can get my computer back to normal? Right now I am posting from Windows 7 on the 120GB drive.

[baseballer10p]

Ok, I don't know what happened, but this morning, I plugged in the 750GB hard drive, and the DVD drive, and somehow the computer booted from the Windows 7 DVD. I ran startup repair, and it restored my computer to an earlier time. It seems that the Fallou3 1.7 update is what caused the problem, because that is no longer installed and my computer boots up fine now. It's also the only thing I remember installing before Windows crashed.