Got access to a xbox or xbox 360? If so you can hook the drives up to it and just log in and see the size. You can hook the old hard drives to the new 360s but you need a cable if I recall correctly. I upgraded to a 360 and one of the newer 250gb drives, but before I got the 250 drive I was using my old one with the 360. I think it was a 20gb cause it didn't hold a whole helluva lot.
Can you post a pic of some of the xbox drives? Might help in narrowing it down. I know we got a few gamers on here besides myself. :P
Far as personal info at lest on the original xbox ones..You could find various personal info like cc #'s, billing address, name, etc. Maybe some old games, and music. I didn't do a lot of buying through my original xbox but I do on my 360. The CC #'s were kept on file on the drives for the ability to renew your xbox live subscription, or for DLC (downloaded content). I know on the 360's all this info IS on there. If I ever get rid of mine, it'll be scrapped and destroyed like any other Hard Drive. Nowadays with a 360 you can download/rent/buy movies, videos, tv shows, games, music, etc. Not to mention your log in info for various services like netflix, hbogo, hulu+, etc.
Hope this helps and if not, chalk it up another late night ramble by yours truly.
Sirscrapalot - Gamer and scrapper.
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