It works with Office 2003 and SQL Server 2000, some quick code to do this is shown below. Finding the location of the Office 2003 key is a bit of a hack, there may be a more elegant way. The code would need error checking added before being put in to production use.

$offkey = "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\11.0\Registration"
$offkey = $offkey + "\" + EnumKey($offkey,0)
$dpi = ReadValue($offkey, "DigitalProductID")
$key = get_product_key($dpi)
? "Office 2003 Product Key: " + $key

$dpi=ReadValue("HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\80\Registration","DigitalProductID")
$key = get_product_key($dpi)
? "SQL Server 2000 Product Key: " + $key

It probably works with other Microsoft products but I don't have any others installed to try it with.