It appears as that the two browser installations use their own profile folder. As far as the two Firefoxes are concerned you have two identities. I somewhat doubt that the profile manager will pick up on the two different profiles, but you can try it by running firefox.exe -ProfileManager. You should see two entries and you can select which one to use. Which one is which is hard to tell and you'd need to try it out. The profile manager will allow you to modify which profile folder to use so that you can tweak the default profile for each installation to look at the same profile folder. Unfortunately, you will have to pick one profile and drop the other. I don't know if there is a way to merge profiles.

Additional information from here http://support.mozilla.com/en-US/kb/Profiles may help as well.

If you are using the same profile with the 3.6.x and 4.0 version then you should create a new profile exclusively for the Firefox 4 version and create a desktop shortcut with -P "profile" appended to the target to launch that profile. The sqlite files in those versions are not compatible and may cause dataloss.

• http://kb.mozillazine.org/Testing_pre-release_versions

• http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows
• http://kb.mozillazine.org/Shortcut_to_a_specific_profile
• http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox

Thank you both for your help, but neither of those suggestions explain why all my cookies are still gone when I go back to using 3.6.15... Any ideas? Thanks again!