Well, here's how it happened.
He gave me the USB HD so that I could back up stuff off my single failing hard drive. I get the new hard drive today, take the failing one out, insert new one and boot up with windows disk. Here I was thinking that since there was only one hard drive in my system the partition crap would require no brains, so I used no brains. =\ Unfortunately, Windows setup detected the USB drive and I accidentally deleted its partition.
COMPLETELY forgot about the external, hadn't touched it in a couple of days since I had finished backing up my stuff.
So yea, not only is some of his stuff on it, but a lot of mine too.