I'm not sure whether discussing a copy of a Windows CD will really be allowed here, it's a very grey area (possibly even completely illegal), even if you do happen to have a license on your laptop. If you have just burned an illegal copy of Windows and are hoping to use your laptop license key to get it to work I'm fairly sure it won't.
To answer your question I've just had a look at my OEM CD and there's nothing obvious that I can see in the directory structure to mark it as OEM rather than retail.