Is this still the case, "AIM 6.8 doesn't provide an option to override the font size of your contacts, which means that you will receive instant messages in whatever size your contact writes them." I have vision problems too and chat with people via their cell phones. They have no way to change the font that they are sending. Is there a registry hack to just make everything bigger perhaps?
AOL AIM Versions
AOL's instant messaging product, AIM, is currently offered in version 7.0. Depending on which version and edition your contacts are using, they may be able to adjust the font size on their end. For example, in AIM PRO, a user can highlight the text and choose the "Set font size" option in the formatting menu's dropdown box.
Changing Font Size in AIM 7.0
AIM 7.0 offers an option to increase the font size. If you haven't upgraded to 7.0, you might want to consider doing it so that you can take advantage of this new feature. Once upgraded and when you are participating in a chat, click the icon with the letter A on it. This opens a menu of different text options including options for changing the font, the font size, text color, background color, and so on. You'll want to click the icon with a two T's on it (on little, the other large). This icon gives you different size options.
You can also change the font size and style for specific buddies in your buddy list in AIM 7.0. However, it's unclear whether these font changes affect incoming or outgoing instant messages.
Enlarging AIM Messages
Another option is to enlarge the AIM messaging window. Depending on the version of AIM you are running, you may see a magnifying glass in the lower right portion of the screen with 100% displayed next to it. Click this icon and to toggle through different magnification levels.
Finally, you can also use the Windows Magnifier to increase specific areas of your computer's display. This tool is located in the Windows Control Panel under the Ease of Access (or Accessibility) section. This tool can be a little tricky to get used to. However, with a little tweaking and experimentation, it may be just right for the job.