You can check for issues caused by a corrupted or incomplete Visual C++ installation that is missing runtime components (Redistributable Packages) required by Firefox, especially VCRUNTIME140_1.dll.

Install both 32-bit and 64-bit "Visual Studio 2015, 2017 and 2019" downloads, (x86: vc_redist.x86.exe and x64: vc_redist.x64.exe) from https://support.microsoft.com/help/2977003/the-latest-supported-visual-c-downloads

You may not need the latter (32-bit version) if you use 64-bit Firefox. You may have to reboot the computer.

When you say reboot, do you mean something like a factory reset, a simple restart, or something else? I didn't make backups before this B.S. happened so I might just be royally screwed depending on what you're talking about. As I've said, I've never encountered this sort of problem before. I have no idea what I'm doing or how to check if this Visual Studio stuff is the problem. I know my computer didn't update itself before I restarted it. I've run virus & spyware scans, but haven't found anything other than 3 tracking cookies. It seemed like a got a new tab in addition to my home tab yesterday evening when my problems with Firefox started which was why I asked if Firefox updated their program recently. Is there any way to be absolutely sure that Firefox has uninstalled everything so that it no longer affects me when I reinstall the thing too? I'm willing to try nearly anything at this point since not knowing what the problem is just makes me more stressed out! Something that's also perplexing me is the fact that Microsoft Edge & Google Chrome still work fine while Firefox just doesn't work! I just can't help thinking there's something I'm missing, but I just don't know what it is!

You may have to reboot the computer.

When you say reboot, do you mean something like a factory reset, a simple restart, or something else?

A reboot means turning off the computer. In many systems, this can be done via the power icon. From the icon, you can select to reboot(restart) or turn the system off.

I have no idea what I'm doing or how to check if this Visual Studio stuff is the problem.

You don't have to check anything. Running the Visual Studio installer will do that for you.

Is there any way to be absolutely sure that Firefox has uninstalled everything so that it no longer affects me when I reinstall the thing too?

If that is necessary, I will instruct you.

I'm not entirely sure, but I think the program is freezing every time I open it but I'm not totally sure. I'm able to click stuff on the menu bar & type in web addresses, but nothing happens when I do either. I'll try the Visual Studio Installer just to be certain that it's not part of the problem too. Luckily my other browsers aren't affected by whatever has happened to Firefox otherwise I'd be royally screwed as I couldn't get online at all!

Ok, I tried the Visual Studio Installer & didn't get any different results. Firefox still isn't even loading the blank tab it starts with. I chose to have Firefox do that instead of restoring my previous session because it was faster. Back when it was working I mean. I mentioned that Microsoft Edge & Google Chrome still seem to work fine because I don't know if that info might be relevant or not. I don't usually use those browsers unless either an addon is really giving me trouble or on the rare occasions where I had trouble with logging in to my email or streaming accounts through Firefox.

hi goryu, try checking out this article: https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can if nothing on the article works, try downloading vcruntime140_1.dll and pasting it into your system32 or system64 folder and restarting your system.

I can't get any of the menu options to work much like how I can't even get Firefox to load a blank tab so I'll check & see if another program might be interfering with it. I already ran spyware & virus scans since I thought of that solution first, but didn't pick up anything other than tracking cookies. I'm using Windows Firewall & Windows Defender though since I can't afford a subscription for any of the paid antivirus programs. I also chose to refresh Firefox so the addons I was using are gone or they should be anyway. I hope I won't need to run that dll program because I've never tried doing that before.

. . . . since I can't afford a subscription for any of the paid antivirus programs.

You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed free to use malware scanners. Each works differently. If one program misses something, another may pick it up.

I'll give them a try. I already have the regular Superantispyware program on my laptop which was how I found the tracking cookies I mentioned before, but I haven't tried other variations of it. I've also gone through my Windows Defender Firewall to be sure Firefox was on the list of exceptions & also added Firefox on the Advanced Security settings. I made sure to be as thorough as possible by looking through my computer for multiple file paths for opening Firefox. I've only found 2 file paths though. I'm not sure if I need to find a way to add the Firefox shortcut on my desktop to the list or not. I've also found that I can open the bookmarks menu on Firefox, but that doesn't really do a lot of good aside from confirming that all my old bookmarks are gone. I still can't open Firefox's settings page or its addon page either. I guess the only thing I can do for now is just download & run different scanners. If there are other possibilities I might've overlooked, please let me know.

Ok, I FINALLY got Firefox working again! I didn't have any luck until I downloaded & ran Malwarebytes' AdwCleaner program. It found some files it marked as "PUP.Optional.Legacy" all of which are registry keys by the look of things. I ran the Microsoft Safety Scanner too, but all it could find were some (apparently) sub-optimal settings for Windows Defender which might help in the future. I was also able to run the free Malwarebytes Anti-Malware Scanner & the TDSSKiller Anti-Rootkit Utility without any issues, but it seems the Superantispyware Portable Scanner has been replaced with a "Technician Edition" which now requires a registration code or Tech ID BEFORE you're allowed to even download it! I thought I should mention that last part since someone should let Mozilla know that they need to update that "Troubleshoot Firefox issues caused by malware" article you sent me. Thanks for your help! If you have any other suggestions that might help prevent this problem in the future, please let me know!

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems. Go to that post and click the 'Solved' button to its right.

I notified an administrator.