"You may not have the necessary permissions" when installing Firefox


When installing Firefox you get a dialog box stating:

“You may not have the necessary permissions to use all the features of the program you are about to run. You may run this program as a different user or continue to run the program as the current user.”

You are given the option to run as the current user or to run as a different user.


This can be caused if UAC is disabled on Vista or by faulty UAC settings in Windows 7.


Right click on the Firefox install file and click Run as administrator.
(Thanks to suggestions in the comments.)

If that does not work then select the correct tab below for further isntructions:
[tabs][tab title="Windows 7"]

  1. Click the Start button.
  2. In the Start Search box, type UAC.
  3. Click on ‘Change User Account Control Settings’.
  4. If it is currently set to Default, try setting it to Never Notify (drag the slider to the bottom) and click OK.
  5. If it is currently set to Never Notify, try setting it to Default.
  6. You can also try setting it to Never Notify, clicking OK then going back into it and changing it back to Default.
  7. Once done, try installing Firefox again.


[tab title="Windows Vista"]

  1. Click the Start button.
  2. Click Control Panel.
  3. In the top right search box type UAC.
  4. ‘Turn User Account Control (UAC) on or off’ will appear. Click on it.
  5. If the checkbox is unchecked then check it and click OK.
  6. It will ask you to Restart. Click Restart Now.
  7. Try installing Firefox again.


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  1. Using Vista, I was not able to check my UAC box, but right clicking and running as administrator did the trick.

  2. I was unable to check my UAC box too, but yes, thank you very very much for the “click with right button on the downloaded firefox and “run as administrator”.” – trick!

  3. I was able to re-install Firefox by running as administrator, but now I can’t even open Firefox. At all.

  4. Win 7: once you have changed your user account settings to “never notify” you also need to reboot for the settings to take effect.

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