This is a tip sent by WebUpd8 reader Bhaismachine. He writes:
On installing MS Office using Wine on Ubuntu, the "open with" menu produces more than one instance of the MS Office apps. I have been solving this issue since really long time on my each fresh install of Ubuntu by opening 'main menu' app and then removing all those entries from 'other' section of main menu.
This is not an issue just with MS Office but with other applications too. To clean the "Open with" menu, right click the Ubuntu menu, select "Edit menus" and on the "Other" section you should find all those Wine applications that show up in the "Open with" menu - delete (forever - don't just uncheck them) those that you don't want to show up on the "Open with" menu anymore.
For Ubuntu 12.04, the main menu application is not installed by default, so firstly you'll have to install Alacarte:
sudo apt-get install alacarte
And then search for "Main Menu" in Dash, and follow the same steps as above.
Thanks to Bhaismachine for the tip and screenshots!