Hello,

What happens if you try opening Firefox as an administrator?

You might not have the correct permissions set for the folder. Which version of Windows are you using?

• For Windows 7 (you can try to see if the same steps work for other versions):
  • Open Windows Explorer, and navigate to C:\Program Files (x86).
  • Right click the Mozilla Firefox folder and select "Properties".
  • Go to the "Security" tab, and under the "Users" group, make sure that the "Read and Execute" row has a check mark under "Allow".
    • If it does not, click "Edit" and give "Users" permission to "Read and Execute".
  • Try opening Firefox again as a regular user.

i am using window8

Have you tried running Firefox as an administrator to see if that works? If it doesn't, then changing the permissions of the folder likely won't make any difference and the problem might lie elsewhere. Right click (you may need to hold the Shift key while right clicking) on your Firefox shortcut (on your desktop) and select "Run as administrator".

If Firefox runs when you are an administrator, check your permissions settings. The permissions settings in Windows 8 should be almost identical to Windows 7. Can your right click on the Firefox folder and see what the permissions are for the "Users" group?

If you don't have the "Read and Execute" permission for the Users group, you can follow the steps in my last post to see if you can change your permissions to allow your Windows account to run Firefox.