An update to my list of what I have done on my end to resolve this issue:

5) I started Firefox in "Safe Mode." Still unable to save as default.

6) I have refreshed Firefox and with the default settings, before installing any new extensions or plugins, Firefox is still not available to become default browser. Firefox V 47.0 32bit gives me error and will not load now. Using Firefox V 47.0 64bit now, but it is crashing.

JEMM5200 said

Firefox V 47.0 32bit gives me error and will not load now. Using Firefox V 47.0 64bit now, but it is crashing.

What is the error? Did you install 32-bit and 64-bit in different folders or is there a possibility that files have become mixed up?

Regarding the crashes: if you are getting the Mozilla Crash Reporter form, your Firefox may have logged some data that would help track down the cause of the problem. You can submit that data to Mozilla and share it with forum volunteers to see whether it points to the solution. Please check the support article "Firefox crashes - asking for support" for steps to get those crash report IDs from the about:crashes page (or from disk), and then post some of the recent ones here.

Update:

I gave up on both Firefox V 47 32 & 64bit, and also Firefox V 48 32 & 64bit.

I did the most complete uninstall of all remnants leftover in the registry and started from a clean slate.

I now have installed in one PC, Firefox V 49.0.

The two major issues I had with the previous versions of firefox mentioned above, not able to be set as default browser and the info sent to Mozilla about the awesome bar taking over the Toolbar and pushing most extension icons off the Toobar, into a dropdown menu have been resolved for the first and second day of use.

Day 3: The ugly issue of Firefox browser not being my default browser is back and just like it was in V 47 & 48. Something has changed in just a short time.

I am back to square one, now I have to go back to troubleshooting on my own, and this really stinks.

Does anyone have any ideas on what is doing this? I t is a Mozilla programmer issue or what?

I went to all the trouble in the above postings and no one comes up with any kind of suggestions, so I go through all the effort to completely uninstall and clean out the registry and then newly install, and now I have the same problem, again

Surely someone has a suggestion here........?

JScher2000,

Even though I am done with V 47 & 48, since you were kind enough to be the only response on this forum of many users and knowledgable people, I will explain to you what happened.

V 47 64bit was installed by itself as well as 48 64 bit at Separate times Then as I tried each version & bit change and found out that particular version was not working, I would then uninstall with RevoUninstaller. Then I would install the next up version and repeat the process.

When I went to uninstall V 47 I believe 64bit, I found there was no uninstaller in that Version. Now a new issue.

So I uninstalled it with a forced uninstall in RevoUninstall Pro, but I knew it did not get all of it as bits and pieces that were left in the Firefox folder for this version, even after a reboot.

So I started thinking there were remnants left in the registry that were still possibly giving me problems, so I went through manually and removed all references to "Firefox" and "Mozilla Firefox." I rebooted and then was thinking on what to do next.

I opted to try one more time with the newest edition of Firefox 49 install.......and that is when those two issues in Firefox 47 & 48 disappeared.

Now as for the errors, I have attached the error messages that came after the re-install of of V 47 32bit and V 47 64bit.

The V 47 64 bit gave me error#1 and then would not load. Then I un-istalled it. The V 47 32 bit gave me error#2 & #3 and were script errors. I have uploaded a screenshot of each error. The script errors were what caused the crashes at that time, I believe.

The extensions I use are the same as 2-3 years ago, but of course up to date. I have not seen any scripting errors since installing V 49 with the clean install.

Hope this helps you to understand more.

As for the Crash Report on those issues, I would gladly send them, but when I uninstalled those older versions and then did a new clean install of Firefox 49, it installed a new profile and unfortunately there are no crash reports on this new version.

I looked through 4 previous profiles I kept in a backup from previous installs, just in case kind of thing, and checked the crash folder and find not one report of any crashes. Why would this happen?

That's about it for those versions and now I have to keep plugging on with the issue back of default browser in the new V 49.

Thanks for your response!

Hmm, I have to admit I haven't tried installing 64-bit Firefox, so I'm not sure of the complications of going back and forth between 64-bit and 32-bit builds. Are they going into the same program folder or different program folders? Customarily on 64-bit Windows:

64-bit programs install under:

C:\Program Files\

32-bit programs install under:

C:\Program Files (x86)\

If they end up overwriting one another, it's possible there is a mixup of files that could break Firefox.

Regarding missing crash reports, they would have been under a different path which most people probably would not back up if they were being selective:

C:\Users\username\AppData\Roaming\Mozilla\Firefox\Crash Reports\submitted\

Regarding the unresponsive script warning, I'm a little surprised by the address (support.microsoft.com) as I haven't seen that one mentioned before.

We have a general support article addressing potential solutions to this issue: Warning Unresponsive script - What it means and how to fix it.

Another common cause of unresponsive script errors on Windows 7-10 is the protected mode feature of the Flash player plugin. That feature has security benefits, but seems to have serious compatibility issues on some systems. You can disable it using the Add-ons page. Either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Plugins. On the right side, find "Shockwave Flash" and click the More link. Then uncheck the box for "Enable Adobe Flash protected mode" and try that for a day to see whether it helps.

Hello again and in response to jscher2000,

Thank you for the responses.

First of all, I was not aware that 64bit programs should be installed in the C:\Program Files\. Is this a rule of thumb for Win10 or any Win version for that matter?

I am currently using Firefox V 49.0.1 32bit on both my PC's and this version seems to be more stable then the others mentioned in my earlier posts. Both PC's have Firefox installed in C:\Program Files (x86.)

I am no longer getting script errors. I am still using the same extensions & plugins as before.

My reason for updating this forum is about the default browser issue. I am still having the same issue with Firefox not being allowed to be my default browser in Win10. This gets so disgusting after this length of time and still not being able to resolve something that seems from a user's point of view, that it should be a simple resolution.

This particular issue only exists on one of my PC's.

Here is what I have worked on, trying to resolve this issue:

1) I had tried to set Firefox by way of settings: through the browser itself, which takes me to settings, default apps and choose the web browser. This way failed because Firefox is not in the options list to choose from.

2) I have tried to set Firefox by way of settings, choose default apps by file type and choosing htm/html and Firefox is not in the options to choose list. Only the same 4 browser options are listed as the options, as seen in my uploaded screenshot.

3) The third way I tried was by way of settings, choose default apps by protocol and once again, Firefox is not in the options to choose list.

4) I have also tried by settings, system, default apps, and scrolling down and clicking on reset in which all apps have to be manually reset, like from scratch in Win10 and Firefox still cannot be found in the list of browser apps to choose from. (Extra work on my end for nothing, but still had to try it, just in case it might work.)

I honestly don't know what to try next or where to go from here to resolve this.

I have uploaded screenshots of what I get when trying through the Control Panel by way of settings, to set Firefox as my default web browser and by way of settings, default apps, web browser etc.

One thing I recently noticed, that I had not checked on before is that Win10 does recognized that Firefox is installed is by control panel and uninstall programs. There it surely shows this version is installed and can be uninstalled. I only mention this because, for sometime, I have been questioning whether Win10 was even recognizes that Firefox is installed and a functional program.

So, I have updated this forum as to the steps taken and yet still no success as to resolution of this issue.

I have other issues that are big woes too with Firefox, but I will do a new posting and different topics for those.

Thanks again and I am still waiting for steps to fix it!

Hi   !
This must be so frustrating for you   ! Went to check my own apps and control panel and   Mozilla is there,   like it's supposed to be. Why it isn't in yours is beyond me, after all that you have done. Shot in the dark: Post this question here:
answers.microsoft.com/en-US/windows/forum/windows_10
(it's a support forum which is similar to this forum)