To look at what profiles are being used and to determine their age, got about:profiles page. You can delete the profile from there if you want to.

Going to about:profiles showed the new profile being used and did not show the old profile which I copied back to the Profile folder. AND it said that I CAN NOT delete the profile being used. I still need a way to CHANGE from the new profile to the old..

If the profile isn't listed in the profiles.ini file then you will have to remove the profile manually yourself.

Note that Firefox uses two locations for the Firefox profile folder (AppData\Roaming and AppData\Local).

Location used for the main profile in "AppData\Roaming" that keeps your personal data.

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>\

Location used for the disk cache and other temporary files in "AppData\Local".

• C:\Users\<user>\AppData\Local\Mozilla\Firefox\Profiles\<profile>\

Are the profiles.ini and about:profiles basically the same piece of data?

I checked both the Roaming and Local folders and the same two profiles are in each; one new created by FF when I installed the latest version yesterday and the "old" one which I had separately backed up and then copied back into the Roaming folder. The dates on the profiles were different in the Local folder, with the 16th on the new profile and the 15th on the old profile. In the Roaming folder, they both had the same date of the 16th since that is where I restored the old profile.

Before I deleted FF, I also backed up my bookmarks per Mozilla's protocol and I restored them with no problems. So at this time I am actually wondering if I need to worry about which profile is being used since FF seems to be working fine. Is there anything I need to worry about in the future? Is this really a non-issue and should I just fuggeddaboutit ? Or keep spinning my wheels?

My real concern is whether the profile chosen may have an impact on my ability to get Avast Passwords to work with FF.

Yes. The about:profiles page shows the data stored in profiles.ini plus some extra data like the full file path of both the main profile folder and a possible second location for the disk cache.

If you want to be able to check the old profile then you need to register this profile in the profiles.ini file. You can do that by editing profiles.ini or easier to use the Profile Manager to create a new profile and use "Choose Folder" in the second window to browse to this not listed profile.

Note that you should never use "Choose Folder" to specify a folder that already contains files that do not belong to Firefox (i.e. only use "Choose Folder" to recover an orphaned profile that isn't listed in the Profile Manager).

Before I register and try the "old" profile, one last question; I just fixed the issue between FF and Avast that caused this re-install of FF and subsequent small problems. Which means that if FF is currently using the NEW profile, will I lose the fix I just put in place if I switch to the OLD profile? I would just like to know ahead of time, so I don't go off the deep end..

And then where do I find the Profile Manager?

Thanks....

Management of profiles is explained in https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles. If the 'fix' you performed for issues with Avast involved editing your profile then you need to repeat them with the new profile. But before that check if it works without any modification.