Login Scripts in mixed NT/2000 domain

I am currently converting all our client systems from Windows Nt workstation to Windows 2000. We use An NT 4 server. I need to have a seperate section in the login script for NT WS and 2000 for installing various programs or patches however when I use The %0S% variable it does not work because the OS in the set command for windows 2000 is listed as NT as well. Is there a separate variable I am missing to allow me to do this. I am new to scripting so if someone can help me out or point me in the right direction I appreciate it.