Triton has usually been the one famous for being a resource hog.
Have you tried a version other than 5.9?
Make sure you are completely removing AIM:
Run the uninstall from Add/Remove programs, and go to your Program Files directory and delete the AIM directory.
You can try 5.5:
http://xeons.net/aim/versions/Install_AIM_5.5.3590.exe
Also run AIM Fix (removes AIM virus's. I doubt this is the problem, but you might as well try):
http://www.jayloden.com/AIMFix.exe