In the box, you will get COA, and product code will be supplied also. License certificate is the COA.

And you're correct in that the OEM version dies with your old computer. And the retail version you can use on one computer at one time. In other words, it can't be installed on two computers.

$242.63 is a good price, but make sure it's legit. There are a lot on Ebay that aren't even though they say they are. Make sure the one you get is, and is sealed.