I just did a fresh install of Mountain Lion on an empty partition. How can I prevent the programs of the previous install from being shown in the contextual menus in Finder ? I already asked Spotlight not to index that partition, but I still have references to them in the Open With menus.
Try rebuilding the launch services database using the
lsregister command. That database provides the information for the open menu, etc as noted in How to rebuild the LaunchServices database from Macworld's Mac OS X Hints. Rebuilding the launch service database while running from the newly installed partition should fix the problem of trying to open Applications on the other drive partition.
If your "Open With" menu shows applications that are no longer installed, or shows some of them as duplicates, you can use the following Terminal command to rebuild your LaunchServices database:
For OS X 10.6 and later run:
/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain system
For OS X 10.5 and older run:
/System/Library/Frameworks/ApplicationServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user
If the problem persists after running the above command, try un mounting your original partition before running the above command again. Additionally, as noted on the hints article and when running the
lsregister command with no arguments there is some helpful output that will allow further customization to specify where to look for Applications, etc.
Is it possible for you to move them to another drive or remove them? If you really want to keep them on the drive that they're currently on you can also make them, or the folder that they're in into a .zip file.
Or if it is just about specific applications that come up all the time in the Open With... menus, then this link will show you how to remove specific applications from the Open With menu.