The problem was that I couldn't touch the drive with any programs or Disk Management utility. I was trying to find the hd_kill.com file that robricc had sent me a while back for erasing drives, but I think I got rid of it for safety reasons. I found a similar, but not as good utility at www.killdisk.com. It was really slow, though (took about 1.5 hours to do 25% of the disc, so at that point I stopped it.

However, I think that's all it took. Now at least Disk Manager recognizes the drive, and I'm currently using Partition Magic to recreate the partition. Everything should be back to normal soon, therefore you should expect another post later with me screaming about how my computer exploded and caught my house on fire.

Thanks for all the help!