"When opening up files in Finder, particularly documents or pictures, you may often want to use an application other than the default one. To do this, you simply Control-Click on the file and choose the application you want from under the “Open With” menu. Sometimes this list contains useless applications that you deleted long ago, which makes the very useful tool slower and less effective.
Getting rid of old applications from this automatically populate list is pretty simple, and is done by simply deleting a single file. This file is located in Home/Library/Preferences, and is called “com.apple.LaunchServices”. Simply locate this file and delete it, and the list should be fixed."
from MacTips.
