This should be moved to the OSX forum, but:
Resetting the 'Open With' Menu
Resetting the 'Open With' menu will remove duplicates and ghost applications (ones you have deleted) from the list. You reset the 'Open With' menu by rebuilding the Launch Services database your Mac maintains. There are multiple ways to rebuild the Launch Services database, including third-party system utilities like Cocktail and Onxy.
If you don't own a system utility that can rebuild the Launch Services database, don't worry; you can perform the rebuild yourself using Terminal.
Using Terminal to Rebuild the Launch Services Database
Launch Terminal, located at /Applications/ Utilities/.
For OS X 10.5.x and later, enter the following at the Terminal prompt:
/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user
For OS X 10.3.x - 10.4.x, enter the following at the Terminal prompt:
/System/Library/Frameworks/ApplicationServices.framework/\Frameworks/LaunchServices.framework/Support/lsregister \-kill -r -domain local -domain system -domain user
The above is one command and is entered on a single line. You can simply copy/paste the above command into Terminal, then press Return/Enter to execute the command.
The rebuild process can take a minute or two. Once the Terminal prompt returns, you can quit Terminal.
Now when you use the 'Open With' menu, you should see an application list that's limited to the applications currently installed on your Mac, with no duplicates or ghosts.