A while back, maybe a year ago I was playing World of Warcraft (in Wrath of the Lich King)
This was before they required using a battle.net account login to, login.
In game somebody told me to enter a code in that would give me an item in game, on battle.net.
Being the idiot I am, not knowing why I did it, I entered it in. After I submitted the code my account got linked to theirs, under a battle.net account.

I basically had no way of proving the account was mine anymore. At the time I pretty much just said "Forget WoW" and quit so it wasn't a big deal.

I ended up getting Cataclysm today as an early Christmas gift after saying I was wanting to go back. I tried to re-enter my old CD Keys from the previous expansions but it said they were already used (On my old account that was hacked)
So I basically have Cataclysm sitting here without a use.

My question is, do I have to re-buy BOTH "The Burning Crusade" AND "Wrath of the Lich King" again?
I was told I could just put in the CD key from "Cata" and it would upgrade my account straight to it, but it didn't work.
And its not like Blizzard will help seeing as its been a year, year and a half. I doubt they would.