How to authorize ADE on a new PC?

I got a new pc (windows7)..had ADE on old pc. Downloaded ADE 2.0, used same used ID & pw that I used on the old pc. Get Adobe error msg.

"You can only authorize this computer (new pc) with an Adobe ID that has not been used previously used on another pc".

I'm sure this happens all the time, people get new pc's etc.

Any suggestions?

Thanks