Maximum PC

A couple of months ago I bought a copy of Windows 7 64 bit OEM and a new hard drive, intending it to be the drive running the new copy of windows on it.
My old drive that had windows xp on it was starting to go bad. I then made my old drive the secondary drive so I could get the data I wanted off of it.
When I installed windows 7 onto the new hard drive I made sure it was being installed to the new drive and not the old one, even windows designates the new hard drive as the one it is installed on.
Now my problem, in my bios when I set the new hard drive to boot up first, it goes to the secondary first. So I switched the boot priority so that the secondary booted first and it worked.
Well today I put a different hard drive in as the secondary and got rid of the old secondary since it was going bad. Now windows goes to the blue screen of death prior to the splash screen and restarts. So I put the old drive back in and it booted, pretty much acting like the old secondary drive was actually the drive which had windows on it, but another twist. Windows doesn't recognize the old secondary drive so I know windows isn't stored on that drive, I think it finally went bad. What in the world is going on?
By the way the new hard drive with windows on it is sata while the old drive is a pata. Another funny thing is that the dvd rom that is hooked up with the old hard drive doesn't show up now in windows.

Unplug the IDE (Parallel ATA, otherwise known as PATA) HDD. What happens now?
Can you post a screenshot (use a camera) of the BIOS?
Have you tried booting from the Windows 7 DVD and running startup repair?

I figured it out. When windows 7 loaded on my primary hard drive, it detected the boot manager from windows xp and it didnt install its own. So once the secondary hard drive was taken out with xp on it windows 7 had no boot manager to load it.

I did this once with Linux, but because Linux wasn't involved, I didn't think of it.