NT logon Script Issue…

I am trying to automate my McAfee virus definitions and the script I am running needs to decifer between Win9x machines and Win NT/2000 machines so it will run a different script. What I have now is this:

if “%OS%”==”WINDOWS_NT” goto :NTUPDATE
if not “%OS%”==”WINDOWS_NT” goto :WINUPDATE

:NTUPDATE
\\AAI_AH_PDC\NETLOGON\NTUPDATE.BAT

:WINUPDATE
\\AAI_AH_PDC\NETLOGON\WINUPDATE.BAT

This script is not working can anyone help???