Are you a student? You can get an upgrade copy of Win XP Pro for less than $90 from
www.newegg.com if you qualify for the academic version. All you need is an old Windows disk (from an upgrade eligible version - I used my old 98SE disk) from
anyone. The only difference between that version and the non-academic version is the price.
The install program for XP asks you to insert the disk during an early step in the process, just to check. As long as you can do that, you'll have a fresh version of M$'s latest OS on your new disk. And you will NEVER need the old OS disk again.
I have to say, I hate Microsoft but I am quite pleased with Win XP Pro. Very stable, MS finally figured out how to allow most programs to install without a reboot (unless it's hardware related), System Restore is a godsend (I just used it last night to squash a gremlin), and they finally got Memory Management right.
On the down side, it is quite bloated: you need at least 128 MB of RAM (should have 256 in reality) and a couple of gigs of HD space. Not that HD space is hard to come by now. But if you don't have hardware that can support that, I'd suggest finding a friend's Windows 98 disk and install that.