Not sure if you can do this, but if you open up disk utility, you maybe able to see the second "unused" partition and format it using HFS+. If this is going back to your time capsule question, keep in mind if you get a NAS enclosure, you will not be able to do this. Since the NAS enclosure is technically a server. The unit itself formats the drive and stores data in it's own way.
Well, if you happen to find a non-Time Capsule, non-Airport solution, let me know. I'm avoiding both products because of the feedback given in the Apple Store. I'm not so much concerned with the reports of "slow backups" as I was about the reports of dropped connections.
Avoid the AirPort Extreme Wireless Base Station. Mine just quit working after about six months of use. Sad. WAN port went out I believe from all notes here on the forum. Worst part is I paid $200 for it because I wanted an Apple produce when I already had a Netgear; I am now using the Netgear. I do think the Apple AirPort Extreme was faster with better reception everywhere, but if it is going to tinker out after six months it is NOT worth that kind of money.