Yep, you can just upgrade your account to a CE version on the account
management page. Belfaire's been out of it awhile. ;)

It's also important to note that when you upgrade to a CE, the
original non-CE code is essentially lost. You don't get it back.

still seems like an incredible waste of money. It's not like you get that standard edition key to use on another account or whatnot.

I was impatient and did exactly this with Wrath of the Lich King. It may seem like a waste of money, but when you REALLY want a CE copy, but it hasn't arrived yet, you'll find that you also REALLY don't want to be left in the dirt with levelling. Might seems a bit drastic, but if people can fork out God-knows how much for an imaginary horse that sparkles, getting to play the expansion with everyone else seems way more worth the price!

"You don't even need to call them. Last time I called, they just said go to acct. management - and enter the code in. I did that for both Burning Crusade and Wrath of the Lich King."
No. Do not follow that bit of advice.

CALL THEM.

If you do the upgrade over the phone and request it, they will give you a standard edition CD key back via email to replace the one your collector's edition key is overwriting. I bought the CEs of both BC and Wrath last year and upgraded my account over the phone with Blizz. They emailed me standard keys for both editions.

You can use these keys yourself for another account, or pass them on to somebody else.

Confirming that you can enter in the Collector's Edition key and it will upgrade your account. However, you won't get credit for a bonus version of the regular edition like you should, so you should probably call anyway.

I didn't know about the calling trick before now--does anybody know if you can call in after the fact and get a code back?