My personal choice wouldn't be something with very much density. I don't want it to fail on me later on, cause I know people who've had failed hard drive after failed hard drive. So I would stay away from anything higher than 40GB. Besides, my current one, an old 27.2GB maxtor from a couple years ago, is way more than enough storage for me already. I haven't tried to clean up space very much, but even so I don't think I've ever gotten past the 20GB mark. Usually I'm around 12GB-16GB at most! I'm building a system identical to yours--gigabyte kt333/1800+/etc. and I think it would be wiser if I were you to go with a smaller, faster drive that's dirt cheap too. Your MB has on-board RAID, how about getting 2 fast 20GB drives (I'm not up to speed on the current drives out there right now so I can't recommend anything) and using RAID 0? It would probably cost you $140/150 total including shipping.