This script uses WMI to determine whether the system is a PC, laptop or server (download):

'Help Now Consulting
'http://www.help-now.com/
'Josh Cook

Set objShell = CreateObject("WScript.Shell")
OS_Product_Name = objShell.RegRead("HKLM\Software\Microsoft\Windows NT\CurrentVersion\ProductName")
OS_Product_Type    = objShell.RegRead("HKLM\System\CurrentControlSet\Control\ProductOptions\ProductType")
Set objShell = Nothing

'Test for Windows 2003 Server (and hopefully above)
If InStr(1, OS_Product_Name, "server", 1) Then

    WScript.Echo("Server")
    WScript.Quit(1003)

End If

'Test for Windows 2003 Server
If InStr(1, OS_Product_Name, "windows 2000", 1) And LCase(OS_Product_Type) <> "winnt" Then

    WScript.Echo("Server (Windows 2000)")
    WScript.Quit(1003)

End If

strComputer = "."
ComputerType = "|"

Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2") 
Set colChassis = objWMIService.ExecQuery("Select * from Win32_SystemEnclosure") 

For Each objChassis in colChassis 

    For  Each strChassisType in objChassis.ChassisTypes 
 
        ComputerType = ComputerType & strChassisType & "|"
 
    Next 
 
Next 

If InStr(ComputerType, "|8|") Or InStr(ComputerType, "|9|") Or InStr(ComputerType, "|10|") Or InStr(ComputerType, "|11|") Or InStr(ComputerType, "|14|") Then
   
    WScript.Echo("Laptop")
    WScript.Quit(1001)
   
Else
   
    WScript.Echo("Desktop")
    WScript.Quit(1002)
   
End If