another how to undo dual boot on 2 drives

After a rash of hard drive failures first on d drive, then on c, I finally have things working again. But with dual boot. My choices are win7 and win7. The first choice works, the second fails to boot.
No idea how this happened. Fustration was setting in.



Can I do as described elsewhere? ie mark c drive as active in disk management, then run startup repair 3 times?
My question is, do I unplug the d drive, or just leave it in?
D is just for documents, should I do anything to clean it up?
thanks

Follow Barefoot's advice to mark Data drive Inactive using Diskpart, then mark Win7 drive Active, before unplugging data drive to run Startup Repair up to 3 separate times.

In addition I would swap the data drive's cable to the Win7 HD so it becomes DISK0 since this problem started because Win7 installer writes the System MBR to the first available Active drive. Be sure Win7 HD then is set as HD to boot first in BIOS setup, after DVD drive.

Good stuff. Thanks so much. Well, when I swapped out the drive cables, the F drive labelled 500GB IDE got in ahead and became Disk 0, not my system c drive. It is an IDE drive whereas the other 2 are Sata. Finally, I just disconnected it, went ahead with the repairs mentioned above. Everything went fine.



So far so good, everything works. Now that third IDE drive, I was thinking of using it as a Win 7 backup drive. Can I just plug it back in now?

Yes, should be no problem as long as it doesn't bump WIn7 HD out of first HD to boot again.

If so, just set Win7 to boot first in BIOS setup (after DVD drive).

This works. And C:system is staying put at Disk 0.
In the future though, I'm not going to mix up sata and ide drives unless maybe the operating system is on an ide drive. And it also wasn't a good idea to make my system drive and data drive the exact same make and model, because now I can't tell the difference in bios. I have to guess at which is which by the order they come in.
It's been a good learning experience.
Thanks all.

Learning is the most important part of it. Good work.