Once I downloaded the 64bit version of firefox 57, I have been able to set it as my default through firefox itself. However this still does not answer why it was altered in the first place after the chrome download and why there are still two entries for firefox in the default programs!

Have you gone to Add/Remove Programs to see if they are still listed there ? It should show version # also, post it if nothing works. If so uninstall, you may get a error saying already did so do you want remove the icon, say yes. Remove all instances of Firefox. You will have to reboot after any changes.

https://www.howtogeek.com/137483/beginner-geek-7-ways-you-can-change-default-applications-and-file-associations-in-windows/

If you do do a uninstall this the best way : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved.

Reinstall with Current Release Firefox 57.0 with a Full Version Installer https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.

Under Add/Remove Programs, there is only one listing for Firefox. However, under "Set Default Programs" there are two listings for Firefox. On my computer (Windows 7 Pro) the two entries look absolutely identical. I was sick of Firefox crashing all the time, so I just changed the default browser to Chrome successfully, but I still want to know why Firefox is listed twice under Set Default Programs, despite there being only one Firefox listing under Programs!! Could this be related to why my Firefox crashes a lot?

P.S. I have no idea why my questions posted twice. (I tried to erase one, but can't figure out how.)

Maybe you have both a 32-bit and 64-bit Firefox version installed.

• (64-bit Firefox) "C:\Program Files\Mozilla Firefox\"
• (32-bit Firefox) "C:\Program Files (x86)\Mozilla Firefox\"

If I had both 64-bit and 32-bit versions installed, I would have expected there to be two listings in the “Add/Remove Programs” Window. However, only one entry appears and it is a 64-bit version. It is only in the “Set Default Programs” window that there are two entries for Firefox, and these listings don’t specify if they are 64-bit or 32-bit.

(While we're at it, when I try to use the "bold" and "italic" buttons in this reply window, why do I get quotation marks instead?)

That is how the markup works on this website. Two single quotes is italic and three single quotes is bold.

• https://support.mozilla.org/en-US/kb/markup-chart

(Although it is not the main question, I appreciate the response about the “mark-ups” – but this does not clarify it for me. When I use other programs and block a word, and then select the “button” for “bold” – the word changes to bold. But when I do that here, it doesn’t change to bold – instead, it acquires quotation marks. Now, what is not clear to me is: After I click to post the item, will it THEN change to bold, or will it still have italics?)

(I can try it here to see, I suppose:  TEST OF BOLD BUTTON)

(I answered my own question - I now see that, although while still in the "composing" stage, when I click the bold button, it does not change to bold until I post it.)

Back to my original issue - I have only one Firefox entry under "Add/Remove Programs" - and it is the 64 bit version of Firefox. It is only when I am in the other window - where you "Set Default Programs" - that two entries appear for Firefox, and in this window the version is not specified.

There is a Preview button that allows to inspect the resulting markup.

(Thanks for the additional tip about the preview button.) Again, back to my original question - I was wondering if it could be that whatever is causing two Firefox listings on the "Set Default" section of my computer settings (although only one Firefox is listed in the Add/Remove Programs - which is a 64-bit version) is also causing an additional problem I am having with this supposedly fast, new Quantum version of Firefox. Frequently, when loading pages in new tabs, the pages get hung up (endless "circling"). It would do this interminably, so I end up closing the browser and then re-opening. Usually when it re-opens, the pages will finally load and I can read them. I was thinking that if I did a simple reset or uninstalled and reinstalled Firefox, I might still be left with the two listings in the Default Settings (because when I reinstalled a couple of years ago, this seems to have been the result). I am thinking about using a program like Revo Uninstaller, which would remove all traces (supposedly) of Firefox. Then I would re-install Firefox and hope it would load this time with only one listing in the Default Programs - BUT then I would worry that the currently saved Bookmarks would be lost, since I would be doing a more robust uninstall using Revo. So - I think I might try that, and hope I can re-install the bookmarks from a separate saved Bookmark Folder stored on my computer (if I can figure out how to do that - probably in the Firefox Help section, so I will try that).