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When I try to start Firefox, I get the error message "Windows cannot find C:\Program Files\Mozilla Firefox\firefox.exe

  • 3 replies
  • 1 has this problem
  • Last reply by cor-el

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This problem happened yesterday, 9th June 2020. Apparently it has been caused by a Windows 10 update, according to some of the other answers to the problem I have seen. My desktop PC was working fine before and I have never ever had this problem in the many years I have been using Firefox. What can I do to rectify the problem?

All Replies (3)

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Hello, try these free programs to scan for existing malware, which work with your existing antivirus software:

Microsoft Safety Scanner MalwareBytes' Anti-Malware Anti-Rootkit Utility - TDSSKiller AdwCleaner (for more info, see this alternate AdwCleaner download page) Hitman Pro ESET Online Scanner Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

then, if your laptop in clean try a clean re-install :

Note: You might want to print these steps or view them in another browser.

Download the latest Desktop version of Firefox from and save the setup file to your computer. After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu). Delete the Firefox installation folder, if exist, which is located in one of these locations, by default: Windows: C:\Program Files\Mozilla Firefox C:\Program Files (x86)\Mozilla Firefox Now, go ahead and reinstall Firefox: Double-click the downloaded installation file and go through the steps of the installation wizard. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

Thank you.

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hello al.hook,

i understand your problem ,

please follow the step and instruction resolved your problem:

Another user reported that moving the contents of:

C:\Program Files\Mozilla Firefox


C:\Program Files (x86)\Mozilla Firefox

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


I hope resolved your problem then mark solution:

Thank you!

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See also:

  1. Open run (Windows key + r)
  2. Type: regedit
  3. Navigate/Search to Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Option
  4. Delete the (Debugger) folders of the apps that do not work