I know this threads kind of old but I was searching for an answer to this question and never found one, so I figured out how to get rid of the AIM Update box on my own. Maybe this will help out somebody else in the future.

Find your aim folder and locate this file, then open it with notepad (you may want to make a backup copy of the file first):

Type Ctrl-F (or go to ‘find’ in the edit menu) and search for this line:

Change ‘true’ to ‘false’, so it looks like this:

Save the file.

The Update box should be gone when you restart the program.