What do you mean when you say I reloaded Firefox ? Did you download another Firefox on top of what you had, or did you Reset / Refresh the current Firefox?

Look on your desktop. Do you see a folder called; Old Firefox?

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Bobert said

I reloaded firefox but first saved a copy of the browser, profile, and plugin files under a different name. I lost most of my addons. When I go to add on Reader, Doubleclicker, and Addblockerplus it states firefox will not allow a file to be changed. When I add and install Tabmixplus and restart firefox it doesn't appear under extensions.

I uninstalled firefox through "add and remove programs" and then reinstalled it from mozillas web site.