try this: - click help>troubleshootinginformation - scroll down to 'profiles' and click 'about:profiles' - if yours is visible, then launch it - if not, click the 'create profile' button, click next, enter a short name for it, then click the 'choose' button to locate and select your profile, then click finish and launch

Thanks for the reply, David. By following your instructions, I've discovered that I have one Thunderbird installation on C:/Program Files/Thunderbird, presumably the latest that I installed by accident, and a second on D:/Thunderbird, which is where I'd put it myself - to complicate matters, I'd also a Thunderbird installation within the latter (D:/Thunderbird/Thunderbird)! Using Revo Uninstaller, I uninstalled the one on the C drive, then the one at D:/Thunderbird/Thunderbird, so I now only have the one left at D:/Thunderbird - if I make a shortcut to D:/Thunderbird/thunderbird.exe, it now works. A bit messy. Should I start from scratch by deleting this D:/Thunderbird installation? (can't Uninstall it as it no longer shows in Revo - is there a built-in uninstall?) Or just leave it as is?

Sorry for making this mess

I would leave as-is. It works. Thunderbird does not rely on registry entries so, if you ever need to remove it, just delete the folder in C:\program files. Life happens...  :)