Spidey,
Believe it or not, most good-sized companies do use proxies to get out to the 'net. Much more secure and easier to track (and restrict) what's going in and out.
Patrician.. If you can browse the web, then your computer has SOME kind of proxy configured somewhere. If you use Netscape, look in the Edit menu/Preferences/Advanced/Proxies. If you use IE, look at the Internet Control panel, connection tab, LAN settings.
One of these two places should tell you what your proxy server's IP (or name) is and the port it uses. You should then be able to configure AIM with the right proxy settings and watch it go.
Just thought of one thing - Most large companies also use proxy config files. If your settings are to "Use Script" or Automatic Configuration for proxies it's a bit trickier. Here's how to find your proxy.
Reboot your machine and don't login to the network, unless you have to.
Open only a browser and leave everything else closed. No e-mail, etc.
Go somewhere on the Internet (Anandtech works nicely, of course).
Open up a DOS prompt and enter "netstat"
It will show you all of your outbound connections.
Look for the "Foreign Address". It's in the form of address

ort. For example, mine says "proxy.mycompany.com:8080". I then know that I need to put my proxy server settings to "proxy.mycompany.com" port 8080.
There might be a few lines listed in the netstat - Your proxy should probably be pretty easy to figure out from them. Many proxies use ports in the 8000 range, so that might be a clue.
- G