Help Determining OS

HI,
 
I am working on a VBS logon script but before it runs the main bulk of the script I want to be able to check the OS the user is logging into so that the script does not run on Server versions. I have found a way to get the information about the OS but if I run the code on Windows 7 and Server 2008 R2 they report the same version number. I there another way to differentiate to two OS's?

strComputer = "."
Set objWMIService = GetObject("winmgmts:" _
& "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")

Set colOperatingSystems = objWMIService.ExecQuery _
("Select * from Win32_OperatingSystem")

For Each objOperatingSystem in colOperatingSystems
Wscript.Echo objOperatingSystem.Caption & " " & _
objOperatingSystem.Version
Next

Thats what I am using at the moment.

Look at the caption property instead of the version.