Hi, If Firefox was downloaded from a known good source, and if the OS is free of malware, then this is most likely a coincidence in that it may be an entirely different issue like hard disk or RAM problems, or a OS problem. You can try to deselect '''Automatically restart''' by right-clicking '''My Computer''' > Properties > Advanced > Settings (beside Startup and Recovery) which may help to give a blue screen. If the blue screen appears you can then search online for the error code which would hopefully help to find a quick solution. The [http://answers.microsoft.com/en-us Windows OS forum] would also be helpful.