Например, так:
Код:

AutoItSetOption("MustDeclareVars", 1)
Local $sComputer = "."
Local $oSWbemLocator = ObjCreate("WbemScripting.SWbemLocator")
Local $oSWbemServicesEx = $oSWbemLocator.ConnectServer($sComputer, "root\cimv2")
Local $oSWbemObjectEx
Local $sDomain = "domain"
Local $sUserName = "username"
For $oSWbemObjectEx In $oSWbemServicesEx.ExecQuery( _
"SELECT * FROM Win32_UserAccount WHERE " & _
"Domain = '" & $sDomain & "' AND " & _
"Name = '" & $sUserName & "'" _
)
ConsoleWrite($oSWbemObjectEx.SID & @CRLF)
Next
Exit(0)