First, are you running the installations from a user with "administrative" privileges? That's required on W2000.
2. Is this happening with only ONE software installation or all installations from CD? If it's a single software, then it's possible the software and InstallShield aren't supported correctly on Win2000.
3. Have you tried creating a folder on the desktop, then "exploring" the CD while it's in the CD-Rom, then copying and pasting ALL of the files from the CD to the desktop folder? Once all files are in the desktop folder, remove the CD, open the desktop folder and double click on the "Setup.exe" file to start the installation. Does that get it installed?
Hope this helps.