Upgrading Free Trial RaF Act. with CD key

I just recruited myself and will begin using the free trial RaF account tonight. When I choose to upgrade the account can I use the CDs and keys for the account I am posting from or do I need to go out and purchase a second copy of Vanilla WoW and also purchase a second set of CDs for the burning crusade?

I plan to pay to keep the two accounts active, but I don't want to have to buy the game and its expansion again if I can save the money by using the ones I purchased for my current account.

Thanks,
-Skid