Or just rip it straight out of ADSystemInfo.
 Code:
Break ON

$objSysInfo = CreateObject("ADSystemInfo") 
$strComputerDN = $objSysInfo.computerName 
$strUserDN = $objSysInfo.userName 

$strUserOU=Split($strUserDN,"OU=")
$strUserOU[0]=""
$strUserOU=Join($strUserOU,"OU=")

$strComputerOU=Split($strComputerDN,"OU=")
$strComputerOU[0]=""
$strComputerOU=Join($strComputerOU,"OU=")


"Information from ADSystemInfo"+@CRLF
"-----------------------------"+@CRLF
"           User DN: "+$strUserDN+@CRLF
"    User container: "+$strUserOU+@CRLF
"       Computer DN: "+$strComputerDN+@CRLF
"Computer container: "+$strComputerOU+@CRLF
@CRLF

Exit 0