Remove duplicates from contextual menus

In addition to Time Machine I do a weekly clone of my system drive to a volume on a second hard drive in my 2011 MacBook Pro. I also made a clone in another volume before I upgraded to Lion.

Now some of the apps from the Snow Leopard drive clone are starting to show up as duplicates in "open with" contextual menus. If I choose one of the duplicates it will open the app from the cloned volume.

How can I remove these items from the menu and make sure OS X doesn't think these are installed apps?

Screenshot:

Rebuilding your LaunchServices database won't do you any good because your computer is seeing the version of the apps on your cloned hard drive (hence the different version numbers). If they were the same number rebuilding the LaunchServices database like answered by others would work.

Your easiest method is to eject your cloned hard drive - this way they won't appear. Telling Spotlight to ignore the drive should tell it from now on to not add the applications to it's list of apps that can open that type of file.

I had the same problem, rebuilding the Launch Services database did the trick for me. Entered the following in Terminal:

/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain user

Then log out and back in. The open with menu should be clear of duplicates.

Credit: https://discussions.apple.com/message/15251482#15251482

Try rebuilding the Launch Services database as described here. Also, it may help to set your backup drive to be ignored by Spotlight (from the Spotlight preferences):