Ve skriptu je chyba, správně je

Const BELOW_NORMAL = 16384
Set objWMIService = GetObject ("winmgmts:\\.\root\CIMV2")
Set colServices = objWMIService.ExecQuery("SELECT * FROM Win32_Service where name='wuauserv'")
For Each oService in colServices    
Set colProcesses = objWMIService.ExecQuery("SELECT * FROM Win32_Process where ProcessId=" & oService.ProcessId )    
For Each oProcess in colProcesses        
oProcess.SetPriority(BELOW_NORMAL)    
Next
Next