It's probably something like this:

Code:
alias windowsdir {
  var %a = a $+ $ticks
  .comopen %a WScript.Shell
  if !$comerr { 
    tokenize 32 $com(%a,ExpandEnvironmentStrings,3,bstr,% $+ windir%) $com(%a).result
    .comclose %a
    return $2-
  }
}