When You are working on AD objects using WinNT the names are NT4 names, so the name for a computer named JDOE will be JDOE$.
The code for Adding computer JDOE to a group would be:
 Code:
$strDomain="Workgroup"
$strComp="jdoe$$"
$strGroupName ="Administrators"

$oDomain = GetObject("WinNT://" + $strDomain)
$oGroup = $oDomain.GetObject("Group", $strGroupName)
$oGroup.Add ("WinNT://" + $strDomain + "/" + $strComp)

-Erik