Using 1TB Drive with Win2000

First, just so you know.... I realize this is an old PC and OS. It's used in an industrial application, not for normal use. The software can't be transferred to another system for various non-software reasons I won't go into it. Anyway.....

I installed a 1TB slave drive and started using it for backup. I know I should partitioned it or something else to be able to use all the space, but had to backup data right away before I could research and see how to do it.

Anyway, now My Computer shows total size 127GB and 2GB available.

My question is.... what can I do to access the rest of that drive? Or is backing it up to another drive and reformatting the quickest way?

Thanks in advance.