Well a bit easier as you only need %WINDIR% which will tell where the WINDOWS/WINNT folder is located.

@DOS 5.0 for 2000 and @DOS 5.1 for XP

And here is a UDF to check the path.

Dim $Path
$Path=RemoteWinDir('some computer')
If $Path
  'Remote Windows directory is: ' + $Path
Else
  'Error getting remote path ' + @ERROR + ' - ' + @SERROR ?
EndIf
 
Function RemoteWinDir(optional $sComputer)
  Dim $sComputer,$WinDir
  $sComputer=IIf(Not $sComputer,'','\\'+Join(Split($sComputer,'\'),'',3)+'\')
  If $sComputer
    $WinDir = $sComputer+Join(Split(ReadValue($sComputer+'HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion','SystemRoot'),':'),'$')
  Else
    $WinDir = ReadValue($sComputer+'HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion','SystemRoot')
  EndIf
  If @ERROR
    Exit @ERROR
  Else
    $RemoteWinDir = $WinDir
  EndIf
  Exit 0
EndFunction