If you are wanting two copies of Thunderbird running, there is an article that addresses that at http://kb.mozillazine.org/Run_multiple_copies_of_Thunderbird_at_the_same_time However, if you will be accessing the two accounts at different times, I encourage you to install one version of Thunderbird and use two profiles if your intent is to avoid having them in same profile. Then, but adding -p to the target line in desktop shortcut, you will be prompted on each launch on which profile to use.