5 Computers Authorized

Just put my 3GS into the MBP and its telling me i've registered this phone to 5 computers, from my memory ive charged it on 2 tower PC's at work and the 3 Macs i've had.

So can anyone tell me how to de-authorize any of the Towers or the Mac's. I guess im going to have to contact Mac to do that bit.

Advice anyone?

Go under Advanced in you iTunes menu bar and choose de-authorize.

If you had authorized a version of itunes on a computer you no longer have or had to reinstall without de-authorizing before hand, you can access your itunes account and de-authorize all you computers, then just go back through and re-authorize on the computers you have.

Done, cheers.