That message refers to an AVG SafeGuard Toolbar extension. Try uninstalling that extension through the Addons Manager. Or maybe try updating AVG to get a newer version of that extension.

Why are you still using Firefox 3.6.4 ?

Mom has an eight year old computer, never upgraded. Attempted to today but couldn't.

Thanks for your help with the AVG add on. I'm going to disable it and see if that resolves the issue. I'll let you know.

That did it, much appreciated!

Posts crossed I see you fixed it. I didn't read the error message closely & missed it was AVG.

If your Mum has any important information such as passwords or bookmarks please as a precaution back up the profile before going any further. Put the backup somewhere safe outside Firefox's program and Profile paths. The Windows Desktop is fine.

• For information see Profiles - Where Firefox stores your bookmarks, passwords and other user data
• Follow these instructions Back up and restore information in Firefox profiles

The current Firefox Release does run on XP. Take care when installing not to use any option to remove personal information. I have not tried updating from fx 3.6 to fx 23 on an XP. You may need to uninstall Firefox 3.6 from Windows XP control panel before installing Firefox 23. (Details aside suggest you are posting from Firefox 3.6 not Fx 5)

• Obtain the installer from http://www.mozilla.org/en-US/firefox/all/
  Use Fx 3.6 or another browser such as Internet Explorer to obtain that.
• see also
  • Uninstall Firefox from your computer
  • How to install Firefox on Windows
  • http://www.mozilla.org/en-US/firefox/23.0/system-requirements/

Thanks all for pitching in to help me out. Much obliged.