Can’t update or uninstall Firefox

While trying to install Firefox 19 over previous Firefox 17 installation the following issue occurred.

Symptoms:

• When trying to run installationpackage for Firefox 19 message appears showing “Your computer must be restarted to complete a previous upgrade of Firefox. Do you want to reboot now?”
• When trying to uninstall Firefox 17 same message occurs.

 

Restarting didn’t make any difference. Same message after 5 restarts.

Solution:

• Delete all files in Mozilla Firefox folder ending with –delete
• Delete file firefox-exe.moz-upgrade in Mozilla Firefox installation folder.
• Run uninstall again, and then install Firefox 19.

References:

http://support.mozilla.org/en-US/questions/757325