ok i did find the SN in that reg key...But its in binary included with a bunch of other info and not easy to notice...But on my pc here its in...

HKLM\System\CurrentControlSet\Enum\Display\<PNPDeviceID>\device parameters

in the EDID value.

If someone has a UDF or something that will convert the binary then you should be able to extract it out.

Code:

$strComputer = "."
$objWMIService = GetObject("winmgmts:\\"+$strComputer+"\root\cimv2")
$colItems = $objWMIService.ExecQuery("Select * from Win32_DesktopMonitor",,48)
For Each $objItem in $colItems
    $pnp = $objItem.PNPDeviceID
Next
$snbinary = ReadValue("HKLM\SYSTEM\CurrentControlSet\Enum\"+$pnp+"\Device Parameters","EDID")
? $pnp
? $snbinary
get $