I was putting in a second hard drive and found out that I had to change the order and when I put it in the computer the first time it came up saying ntldr missing, I tried repair and I don't think that worked because the hard drive went from a 27 gig to 10 mb and says there isn't any thing on it. I need to save the info! All I noticed is that it says the it is a fat drive and not fat32.
The mbr or boot code of the drive might be screwed. Go to the ultimate boot cd and burn their iso to disc. Reboot with the disc in and it will have various tools to fix the boot code and what not of the drive. Good freeware program. Saved me the other day when partition magic screwed up my drive.