Update: everything is fine!

I was able to fix the HD's with a little util Samsung provides for it's harddisks, ES Tool. Essentially I was able to use this utility to Set Max Address and Recover Native Size. This worked like a charm, and now my disks are fully operational with their intended space.
So Mark was correct about the problem (not that I doubted him!), but I was able to fix it easier than his solution. Well, maybe not easier, but faster anyway since I didn't have an Ubuntu system readily available here. All this took was creating a dos boot disk with this utility on it.

Thanks so much for helping me with this problem. I've learnt something new: I had no idea something like "Host protected area" existed!

Thanks very very very very much to all who've helped!