Hmmm... perhaps for some strange reason your drive has already been partitioned? I'd create a basic boot disk with fidsk on it, and boot with that and delete all the partitions that are on it... Then create the one massive partition that you want... (Well, you should seperate the system and data sections, but that's up to you) Fdisk can be a bit intimidating if you've never used it before, so you've been warned... Windows installer partition table stuff is always a bit dumbed down so it's easier but doesn't make things clear.

Matthew