Reset Mozilla Firefox in Windows Xp
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How to reset Mozilla Firefox
Internet Explorer Mozilla Firefox Opera Safari Netscape Chrome
   
Browser Windows Back
Write firefox -safe-mode and press ok
Windows:          
This method shows you how to reset Mozilla Firefox to default settings using a command line.
Please perform the following steps:

Please go to Start and choose Run ...
Up Back
   
Browser Windows Up Back
Please confirm Firefox pop-up  
Make your settings and click on Make Changes and Restart
Browser:          
This method shows you how to reset Mozilla Firefox to default settings using Firefox Safe Mode.
Please perform the following steps:

Please open Mozilla Firefox, go to Help button and select
Restart with Add-ons Disabled...
Make your settings and click on Make Changes and Restart