In this video from AppleGenius0921 we learn how to create a free .mac account and AIM account to use with iChat. Go to iChat and go to Preferences. Click the plus sign in to bottom left. An account setup window will pop up. Click get an ichat account. It will redirect you to apple's site where you can create an apple ID. After you complete that step, go to the plus button again, and set up your new .Mac account that you just created within ichat. Now to make an AIM account, go to aim.com. Click get a screen name in the top right corner. A plus sign to getting an AIM account is that you can use it on Windows and also on all mobile devices. You also get an email account with this as well. To create your AIM account, follow the steps on the website. Then go back to ichat and follow the same steps you did as before, but this time go to AIM account from the drop down menu.