Hi ashiq,

Can you start firefox in Safe Mode by holding down the shift key while starting Firefox ? if yes, then click the Reset Firefox button .

(The "reset firefox" works creating a new profile folder while saving your bookmarks, browsing history, passwords, see the above link)

EDIT, i supposed you have xp sp2, sp2 it is the minimum xp to run firefox, see : Firefox 15 System Requirements

thank you

A possible cause is security software (firewall,anti-virus) that blocks or restricts Firefox or the plugin-container process without informing you, possibly after detecting changes (update) to the Firefox program.

Remove all rules for Firefox and the plugin-container from the permissions list in the firewall and let your firewall ask again for permission to get full unrestricted access to internet for Firefox and the plugin-container process and the updater process.

See:

• https://support.mozilla.org/kb/Server+not+found
• https://support.mozilla.org/kb/Firewalls

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