Thunderbird is designed such that uninstalling does not delete data. Before removing one, I suggest you first verify the location on disk for each version to ensure you don't remove the wrong one. I also encourage doing backup of profile whenever doing anything of substance, if only to protect you from any mistakes you might make. Assuming the normal location of profile, you can do back with these steps: - exit thunderbird - click windows key and 'r' key - enter %appdata% and press enter - that should place you in the appdata/roaming folder - there, you should see a folder named Thunderbird. copy that to a safe place