The big picture is, in fact, that PQ Magic let me make a dumb mistake. I shot myself in the foot with this one, when I realized late last night that the size of the drive was about half what I thought it was. In fact, if the partition table is wrong and says that there are bits available out past the end of where there are really bits, the OS has no way of knowing where to stop writing.
Regarding backups, I am terrible about backups. The really critical stuff -- the wedding pictures -- are backed up to DVD and copies are sent to people who care. Everything else is just a hassle (for the most part) to replace, or would consume a lot of time, or isn't really that critical anyway. I keep all of my film-based work scanned on the computer as well, and it takes about half an hour to scan a roll of film. Re-scanning 300 rolls of film is a monstrous project that I really don't feel like undertaking, but ... if the data's gone, it's gone. I have pictures of my niece and nephew from my time home at Christmas a few months ago, and if I really need them, I think I left copies on my parent's computers before I left ... So if the data's gone ... it's gone. I'd just rather that it not be gone.
I know that in a technical sense, the bits are still there. I've just lost the easy way of getting to them. I would be ecstatic if I could find a way to recover that data -- which is why I'm here getting second opinions before I start manually tweaking bits in the partition table or something.
Paul -- GParted looks like a great tool, I'll give it a shot. In fact, it looks like an open source version of PQMagic, which would make me very happy indeed.
I already have, btw, an interesting tool that allows me to basically insert arbitrary values into the partition table. I could try to take a picture of the current output of that display ... you'd probably all be shocked at the havoc that I've wreaked on this drive. I spend too much time at work maintaining computers correctly to get it right at home, I guess. Anyhow, it's pretty powerful ... I just don't know what values to put in to most likely assure recovery.
SlowToady, you've pulled my fat out of the fire before. If you have a tool you recommend, I'll trust you whole-heartedly.
Thanks again, all.
Dan