What OS are you using? I recently saw just the same in Windows 10 - and when I went to look at the list of installed programs both TB38.5.0 and TB38.5.1 were shown there too. Removing the older version killed Thunderbird outright. I suspect it treated a full install and a later upgrade (patch?) as two separate installations and recorded them as separate programs. (If so, no wonder why firewalls become confused.) I would think that you can delete any shortcuts for TB38.5.0 but not the program itself. In my case, having uninstalled (i.e. deleted) TB38.5.0, I had to download and install the full TB38.5.1 (which is what I routinely do on my Linux machines, so no real hardship). Since doing this doesn't touch the profile, you don't lose any messages settings, address book etc. If you want it tidy, do the same. Uninstall whatever is currently installed, and go get the full installer for the current version. https://www.mozilla.org/en-US/thunderbird/all/ It might be informative to note the sizes of the relevant folders before and after a removal and re-installation to see what space saving is obtained.