Formatting

I recently installed Red Hat Linux 6.0 on a workstation with two hard drives. The one hard drive has Windows NT 4.0, and I put Linux on the other hard drive and used a boot disk when I wanted to use Red Hat. I would like to format the hard drive with Linux on it, but FDISK does not recognize the file system, and FORMAT does not work. How can erase the Linux hard drive? Are there any third party format programs I can use so I can format the hard drive so I can put another operating system on it (Novell, NT)?
Eric Morrison
Systems Administrator
Car-Tel Communications, Inc.
emorrison@car-tel.com