Repost (I hate this time-out problem)
Just want to make sure I undestand your situation.
You previously had Win2K installed on your computer. At some point, because of problems, you decided to re-install Win2K. Instead of doing a repair install, or wiping the drive and starting over, you chose to do a new install in a different directory leaving the previous install in place.
If this is essentially the situation, and assuming you are in fact booting to the new install and it is operating properly, you should be able just delete the OLD Windows folder.
If you only have one Windows folder, then you do not have 2 separate installations on your hard drive. You will not be able to determine which files may have only been used by the old installation and which are being used by the new installation.
Usually when you do a repair install, or install in the same location as a previous install you will nor have very many instances of new files coexisting with old files. Old or corrupted files just get replaced.
A couple places to look for space hogs:
Check the Temp directory both in the Windows folder and in your profile. Also check the Temporary Internet Files folders.
Make sure you empty your Recycle Bin.
If none of the above solves your space problem, you need to do a little sluething to determine which folders are hogging the disk space.
How big is your hard drive? The fact that it is new system does not guarentee you have a large hard drive.