Hey...

Download the relevent 32 or 64 bit release of the previous version from the links underneath, select as per your language

edit: Please go to www.mozilla.org/firefox/all/ for current Release as the links were for the old Firefox 70.0

Should work fine, once installed go options disable automatic firefox updates for time being.

Hope it helps

By the way do you have a AMD ATI graphics chip/card ?

edit: OP asked for 77.0.1 and not the old 70.0

Didn't work. I have 2 drives. C is an SSD. E is what was the original C drive. I store data on E and programs on C (although E still has some of the original programs undeleted). The only instance of a program related to Firefox which I can find with explorer on either drive is Mozilla Maintenance Service which appears in the (x64) section of both drives' Program Files. In C:/Program Files I can find Mozilla Firefox, created today, size 195Mb. Opening that there is a Firefox.exe app file size 565Kb, which when opened says Windows can't find the file. ???

Graphics are integrated on a Gigabyte motherboard.

BTW I am a "silver surfer" - 35 years experience of driving a computer but scant knowledge of what is under the "hood"

Hi jeffbarnes1945, the error you mentioned started affecting a lot of users yesterday for some reason. I don't think we have an explanation for it yet. In the extreme case, other programs under C:\Program Files couldn't run either. Many of the affected users also run Avast, but I don't know whether that is a factor.

One possible workaround is to move Firefox to a different folder. This may help, but unfortunately I cannot tell you what is going on on your system.

Some Other Threads

• https://support.mozilla.org/questions/1290476
• https://support.mozilla.org/questions/1290490 *
• https://support.mozilla.org/questions/1290493 *
• https://support.mozilla.org/questions/1290513
• https://support.mozilla.org/questions/1290528 *
• https://support.mozilla.org/questions/1290534
• https://support.mozilla.org/questions/1290540
• https://support.mozilla.org/questions/1290541 *

Program Move Workaround

The threads followed by * reported that moving the contents of:

C:\Program Files\Mozilla Firefox

to

C:\Program Files (x86)\Mozilla Firefox

allowed Firefox to run. I don't know why that would make a difference.

Moving the program as indicated solved the issue. At the same time I am finding other problems not to do with Mozilla. Seemingly another Windows screwed-up update.

Oh, it was a "patch Tuesday"? Because IT manages my updates I don't get them in real time. This is a good site to check for news on patch issues:

https://www.askwoody.com/category/microsoft-windows-patches-security/