Go to 'View' and un-check 'Hotlist'. Remove them if necessary. You also have to make sure that you use either the 32bit version of AOL and Opera or the 16bit version, but not the 16bit of AOL and the 32bit of Opera. That will NOT work. Opera does not support CompuServe's virtual keys.
Preferences is right on the menu bar at the top of the browser.
If this has disappeared, hold down the Ctrl button and press F11. Upgrade to Opera 3.21, that will fix the problem. Opera is my default browser. Usually from the browser you want to make default. Both Internet Explorer and Netscape default to display a dialog box at startup when the .htm, .html, and http associations point to another browser.