No more than 128GB recognized on a 500GB SATA HDD in Win2k Adv Server.

I’ve installed Service Pack 4, but still can’t see more than 128GB. I’ve downloaded controller drivers, etc. from Dell’s site (the system is a Dell Dimension 8300), but it requires a floppy drive to install and the system doesn’t have one. Furthermore, Windows XP recognized the full 500GB, so it isn’t a motherboard issue.

Any ideas?
~Jasper