I have Thunderbird version 17.0.8 which I have repeatedly tried to update. I'm on Windows 7 Home Premium. I've also tried installing the Lightning calendar, which apparently worked but it won't allow any data entry. In other words, it's apparently there but it looks like a ghost. The update screen for Thunderbird tells me I'm at the update centre but the activity indicator just keeps going round and round ad infinitum. The posted solutions don't appear to address my Windows version, although I confess to being no expert. So the ultimate question is: should I be able to update Thunderbird 17.0.8 and should I be able to use Lightning with it? Many thanks.