Where did you download from? Please go to http://www.mozilla.org/en-US/firefox/new/ and re-download the installer and post back with what happens.

If that doesn't work, the next step would be to see if your av software is interfering with the install

Thank you for your reply. I was directed to mozilla by a window that came up as a reminder, and that's where I've downloaded it........twice now.

I'll try again.

Av software? Not sure what you are talking about?

Anti-virus software - sometimes av software will block applications from running.

I've thought of that, though I'm not sure any new anti-virus program that doesn't predate my last FF update (7) just a few weeks ago?.

Well, I just looked at properties on the FF symbol on my desktop. It tells me that the last time it was modified was on September 28........two days ago. So...is it possible that it upgraded without having to do a restart, and the upgrade just went unnoticed???