Check your Windows Task Manager "processes" tab to see if "firefox.exe" is one of the processes, if it is end it and restart Firefox.

If Firefox still does not start go to the Control Panel, add or change programs, look for "McAfee Site Advisor" or just "Site Advisor" if you have either one uninstall it, then reboot system and restart Firefox; otherwise, come back for more help,

You description appears as if nothing at all happens, if that is not the situation they you need to tell what you do and do not see,

Hi you are correct - nothing visible happens when I click on the icon, however the program is active when I check the procces tab,

I have deleted it on the process tab and it still does not start.

I checked for McFee and site adviser which do not appear to exist.

Since posting my query I have totally removed Firefox and resinstalled it yet I still cannot start it.

-> "Firefox is already running but is not responding" error - How to fix

-> Profile in use

• http://kb.mozillazine.org/Profile_in_use

Check and tell if its working.