Deauthorize All Computers Associated With Your Apple ID

If you are trying to authorize a new computer for your Apple ID (iTunes) and having trouble due to 5 authorized computers then you can follow these steps to deauthorize all those computers. This may be not new to you but I didn't know about this.

1. Open iTunes, sign in to the iTunes store.
2. After signing in, view your account through -> Store -> View My Account. ( You may need to enter your password again. )
3. In the Account Information window, click Deauthorize All.
4. Done!

Now, you're ready to authorize your new computer.
For more information: http://support.apple.com/kb/HT1420