[Helmling]

Oops. They pulled my old computer from work and I forgot to deauthorize it for iTunes. How can I reset my account for a machine I don't have access to anymore?

[GSixZero]

http://docs.info.apple.com/article.html?artnum=93014

If you find you have reached 5 authorizations due to system upgrades, you can reset your authorization count by clicking Deauthorize All in the Account Information screen. Note: You may only use this feature once per year. The Deauthorize All button will not appear if you have fewer than 5 authorized computers or if you have used this option within the last 12 months.

To deauthorize all computers associated with your account:

Click Music Store in the Source list.
If you're not signed in to the store, click the Account button, then enter your account name and password.
Click the Account button again (your ID appears on the button), enter your password, and then click View Account.
In the Account Information window, click Deauthorize All.

Don't worry about it until you have 5 auths and need another.

[Helmling]

Oh, I thought it was 4.

Ok, then, no worries.

But I still resent this feature! You hear me, Jobs! I am unhappy with you...about this one thing...and not much else...so, you know, consider yourself warned!

[parsec_kadets]

I agree, Apple needs some kind of tool, either built into iTunes or web based, that will let you see what computers are authorized and remove old systems. It's just common sense.

[GSixZero]

Do you know your ethernet MAC address off the top of your head? If you do, that info might help, but that's all ITMS knows about your computer.

I don't think a list of MAC addresses will help most people.