How are you sending this email then
Hopefully they will pick up on this and send you an email. I think what you can do is that you can find the mac address and send that to them (Don't do it until the ask for it) but after you send them the mac address off of your Network card (you do have a network card in that system don't you?) they can generate a serial number for you.
When you are ready to get your Mac Address do the following:
Click "START" Click "RUN" type "COMMAND" in the window that opens up type "ipconfig /all" a bunch of information will scroll on the screen. The number you want is the physical address that will look like this: xx-xx-xx-xx-xx-xx
Hope that is what you need