I'm having a similar issue.
I have three hard drives. One old (6years) 150gig, a new 1TB which has XP Pro installed, and a even newer 1.5TB that I have Windows 7 installed on a 100gig partition.
I was fooling around in the BIOS trying to overclock my CPU when I reverted the BIOS back to "stock" settings.
When I did that, I forgot to go back in and make sure that my Windows 7 partition was first on the list.
Therefore, it loaded up my XP. I didn't think it was a big deal, so I restarted the computer, went back into BIOS, and chose the HDD with Windows 7 on it.
During the restart I got an error message saying that the "NTDLR is missing" error message, and it won't boot!
I have the full install disk and have gone into the repair area but when I get to this part:
I don't have any disks that show up. I says if none are showing, to click the "load drivers". I can get into my Windows 7 partition when that screen pops up, but I have no idea what or where the drivers are located????
I need to figure out this step so I can actuall fix Windows 7!
Any help is greatly appreciated!