During the install, you will be asked about where you want the program.

If it can't find your old profile, we can fix that after.

• 1 Download Firefox Full Installer For All languages And Systemsv38.0.5 {web link}
• 2 Uninstall Firefox from your computer {web link}
  DO NOT remove your profiles.
• 3 After, reboot the computer. Then run the full installer.

If you have a profile that doesn't show in the Profile Manager and want to (re)register it then use the Profile Manager to create a new profile and click the "Choose Folder" button and browse to the unregistered profile to make Firefox use this profile.

1. open the Profile Manager
2. click "Create Profile" and read the text
3. click Next to proceed to the window where you can either accept the default or choose an existing folder to use for the profile
4. click "Choose Folder" and browse to the profile folder you want to register

You can give this profile a descriptive name that will show in the Profile Manager if you like. Click "Start Firefox" to start Firefox with the selected profile Note that you should never specify a folder via "Choose Folder" that already has other files in it, but either select a valid profile or an empty folder. Firefox will recognize and use this folder and you will have access to all personal data (bookmarks and other data) that is stored in this profile.

• http://kb.mozillazine.org/profiles.ini_file
• http://kb.mozillazine.org/Profile_Manager

FredMcD said

During the install, you will be asked about where you want the program. If it can't find your old profile, we can fix that after.

• 1 Download Firefox Full Installer For All languages And Systemsv38.0.5 {web link}
• 2 Uninstall Firefox from your computer {web link}
  DO NOT remove your profiles.
• 3 After, reboot the computer. Then run the full installer.

Hi, probably FredMcD means 39.0 version, not 38.0.5.

thanks