Once you uninstall it in Add/Remove programs, start>search and type viewpoint, then look what folder the viewpont exe is in then delete it. You might have to stop a process in task manager to delete all the files in the folder. You can also go to regedit and delete all the viewpoint objects in the registry if you want.
AIM also creates AOL shortcuts that point to a file in a folder that it makes called AOD within program files. I would delete the links and the the AOD folder as well.
For AIM users, Dead AIM is a good program. It takes away the stock ticker, popups and advertisements.
http://www.oldversion.com/program.php?n=deadaim