To uninstall Win2K (whichever version):
- Boot from Win98 boot diskette
- FDISK /MBR (not sure whether necessary, just in case)
- sys C:
Now, you'll be booting straight into Win98. You can delete your Win2K files now - \WINNT, \Documents and settings, the really big file at the root (Win2K swap)
I guess there's a similar procedure to uninstall Win98, but I'm not familiar with it.
-PJ