What did you have installed before?
NT is sometimes hard to get rid of to install win98.
Sounds to me like you need to fdisk your hard drive and start over. I also have a utility called gdisk (get it? fdisk - gdisk?)
that is really good at cleaning a hard drive.
Another idea is to go to the manufacturer's website of the Hard Drive and see if they have doctoring utilities to gut your HD and start over.