Unwanted Programs

I accidentally approved a plug-in program to download when I was downloading from a website. The problem is that now it puts an icon in my system tray, and loads 2 menu bars into my internet explorer. How would I go about getting rid of this and other programs that load at startup, but do not appear in the startup folder? Also it does not appear in the Add/Remove programs. Help would be much appreciated with this annoying and bothersome problem. Thanks.