Can you try to reset your useragent setting? Instruction can be locate here, see Helper7677 's 3rd instruction

• https://support.mozilla.org/questions/760152

You can find the current Firefox version in listed at the top of the "Help > About" window.

• https://support.mozilla.org/kb/Finding+your+Firefox+version

If that is still Firefox 3.5.19 then do a clean (re)install and delete the Firefox program folder (C:\Program Files\Mozilla Firefox\).

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 12.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other profile data are stored elsewhere in the Firefox Profile Folder and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

so what exactly is not working? it seems you still have Firefox 3.5. Let's try this :)

Open Internet Explorer. Go to www.getfirefox.com. Click the Download Now button, then click Run. (Make sure firefox is closed). Follow the steps to install Firefox. You should now be all up to date :) does everything work a bit better now?

internet explorer blocked from downloading files for my protection

Try resetting Internet Explorer, then follow those directions again: http://support.microsoft.com/kb/923737

after downloading FF12.0 there is no place to click run

Wherever you saved the file will have a Firefox Setup 12 file. Just find it, double-click it and run it :)