I use the function getbit that I have made below. Also as a bonus I have provide the function GetOS to show how to use it.

Function GetOS()
	Set objWMIService = GetObject(''winmgmts:{impersonationLevel=impersonate}!\.rootcimv2'')
	Set list = objWMIService.ExecQuery(''Select * from Win32_OperatingSystem'')
	For each obj in list
		GetOS = obj.Caption & '' Service Pack '' & obj.ServicePackMajorVersion & ''.'' & obj.ServicePackMinorVersion
		GetOS = GetOS & chr(32) & GetBit() &  chr(32) & ''bit''
	next
end function


Function GetBit()
	set Reg = CreateObject(''WScript.Shell'')
	If Reg.RegRead(''HKLMSYSTEMCurrentControlSetControlSession ManagerEnvironmentPROCESSOR_ARCHITECTURE'') = ''x86'' then
		GetBit = ''32''
	Else
		GetBit =''64''
	End if
End Function

msgbox getbit()
msgbox GetOS