Start Firefox in Use Troubleshoot Mode in Firefox to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

Thanks for the help but no change. It's still running itself and can be seen on the task running list! I'd used Nod32 and McAfee to check the machine but can't be fixed. It seems no harm to my computer but make me nervous.

See also the about:robots page if that is what you see.

Thanks for your kind reply again, The running program's stop finally after I installed the "Security task manager". It seems really an auto update work for Firefox but I have no idea why it keeps on running for days. At last I force it to stop and it's all over! Now, I still have the question why the thing installed without my notice or control. Sorry for the late reply because of the Chinese New Year! Thank you very much!