Hi,
As EZ Jim says the statement on the second screen in the iChat Start Up Screens can be confusing as it tends to default to a Apple ID option rather than AIM.
This iChat 4 pic defaults to @mac.com being in the Drop down and the lead-in blurb also reads that way
This screen is for entering names that can work with the AIM server.
You will find the "Account Type" item in the middle has a drop down that lists @mac.com (Shown), AIM and MobileMe (Accounts from Apple ending @me.com).
If you have clicked through this part and iChat launches without the Start Up Screens (First Run only) then see this page
http://www.ralphjohns.co.uk/versions/ichatvers4/howtoStartiChat.html at the Alternative section further down (How to add a Screen Name from the iChat Preferences)
More on
Getting a Screen Name
In iChat 5 with Snow Leopard if you select @mac.com in the Start up screen (or in the Alternatives Add Screen Name option) then the Get iChat Name takes you to the @mac.com Registration Page.
If you select AIM in the drop down you get taken to the AIM registration page.
Both these are Free. (The @mac.com one will not works as an email address)
The Getting a Screen Name page also points out about MobileMe. (Costs after 60 days but has other services - IMPORTANT. Requires active discontinuation of the trial or you get charged)
You may also have an ISP that has made a similar agreement to the one Apple did that gets @mac.com and @me.com names recognised as Valid AIM Names and this may also work.
Jabber names.
These fall in to two sub types. Names from Jabber servers and GoogleTalk.
GoogleTalk is based on Google Mail Names (@gmail.com and @googlemail.com) but despite being a Jabber server it does not follow the same Server name Convention others do.
Most Jabber servers cannot be registered "on-line" with a web Browser and require you use a third party Jabber app like Psi that include a Registration Module.
Google requires you enable your Google Account's settings for Talk before the name will work in any IM app that can Login in a Jabber server.
However all Jabber servers give you a name that looks like an Email address as in
username@aJabberServer.com
This fact that both the AIM servers and the Jabber ones use (or can use) IDs/Names that look like email addresses that can lead to confusion when adding your own Screen Name to iChat or adding Buddies later to the correct Buddy List.
NOTES.
I have linked you to the iChat 4 info on the Start Up Screens as the iChat 5 Page link does not work (I Just found out).
There are very little difference in iChat at this point and the Alternatives section also applies.
Adding a Screen name from the IChat Preferences as shown in the alternatives does however give you the choices between the 3 AIM types of names (AIM, @Mac.com And @me.com) iChat can use and the two Jabber types (plain, as it were, and Google).
I may receive some form of compensation, financial or otherwise, from my recommendation or link.
11:35 AM Thursday; September 2, 2010
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
Message was edited by: Ralph Johns (UK)