installing thunderbird is normally safe from affecting the installed profile. HOWEVER, if you are planning to reinstall, I always suggest taking the extra precaution of making a full copy of the profile. That is done in two steps: - be sure that thunderbird is not running - copy the profile, normally at c:\users\<yourid>\appdata\roaming\thunderbird to somewhere else then, if the profile is affected in the fresh install, just - exit thunderbird - copy the saved thunderbird folder back to c:\users\<yourid>\appdata\roaming