And store what? Your OS? Haha, the Seagate or Western Digital hard drives that come with the Xbox are about 8gb-10gb, and they're the old 5400rpm ones. Becides, they software lock it so only the Xbox hardware can use it, meaning that you can't just plug it in and expect it to be an additional hard drive.
WEster digital is more than not worth it. Western digital hard drives are esily corrputed. Seagate is allright too.
Also my hubby's stepbro went and shot one up with a shotgun! big ol slugs! it was funny. it was a 15GB model and it crashed, so he took his frustrations out on it! I thought it was funny. I did not witness the event personally, but If I were there it would have been one of the most funny sights!