I just recently built my computer and bought a Windows 8 x64 OEM disc, and it worked like this.
The OEM box doesn't have your product code on the outside. There may be a red seal to break open. On the inside there should be a case which says Windows on it and has the disc inside. The case which includes the disc should have a product key sticker.
If not, the rich guy didn't include that case and you need to ask him for the activation key.
-------------------------------------------------------
See image attached. The blue circle is the disc which is inside the disc case. The gray large box is the disc case that has a product key sticker on it which is inside the oem box. The large black box is the OEM box.
