Hello stancollins and thanks for contacting us,

The most probable explanation of this issue is that Mozilla Firefox setup files are corrupted. That may be caused by a virus or a damaged hard disk.

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try some of the following programs to scan for malware:

• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility
• Microsoft Security Essentials (A good permanent anti-virus if you don't already have one)

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

After checking you don't have viruses, please open a administrator terminal (system symbol) and type the following command:

chkdsk c: /f /r

where c is your system drive letter.

You will be asked for performing the check the next time Windows boots, because the drive needs to be locked. Type "y" or "yes" depending on what you see on screen and press Enter. Reboot your computer and wait for the scan and fix to finish.

Once you are sure you have no viruses and your drive is healthy, try to reinstall Firefox before uninstalling it (Install it on the same path, so helper.exe is replaced). Afterwards, if you need to, uninstall Firefox as you'd usually do.

Did this fix your problems? Please report back to us!

I don't know what the "system symbol" is. If it's a keyboard key, I don't seem to have one.

I tried running "chkdsk c: /f /r" from the command prompt but got the following: Access denied as you do not have sufficient privileges. You have to invoke this utility running in elevated mode.''

I don't know what "elevated mode" is.

System symbol is the command prompt. About elevation, you should right-click the command prompt link (on Windows 8 type command on Start Menu and right-click Command Prompt tile) and choose "Run with administrator privileges" or "Run as administrator" or similar. Then type chkdsk c: /f /r and you'll be able to check your disk.

After running the chkdsk and re-installing Firefox I was finally able to do an uninstall via the Control Panel. I selected the options to remove EVERYTHING. It seemed to work as my shortcuts were removed. However, the the Program Files folders were not removed. I tried deleting them from the Program Files folder but was told I don't have sufficient permissions to do so, even though I'm logged in as an administrator. I moved them out of the Program Files folder and tried again but got the same rebuff. I even tried deleting them via the Command Prompt using the 'Run as Administrator' feature. This, too, had no effect. How do I get rid of the leftover folders?

Try to start Windows Explorer as administrator by right-clicking its icon. Go to those folders and right-click them. Click Properties and under "Permissions" make sure all read/write permissions are checked. If Windows doesn't allow to enable them, start Windows in Safe Mode.

Starting Windows in Safe Mode may prevent your computer from running any malware or tool that may be blocking some administration actions such as removing a folder, modifying a system file, uninstalling a program, etc.

To start Windows in Safe Mode under Windows XP, Vista or 7, press F8 repeatedly during reboot until a menu appears, and choose Safe Mode. Under Windows 8 you should start (Windows+R) msconfig, go to Boot and mark "Start on safe mode". Reboot your computer and Windows 8 will run safe mode.

Once on Safe Mode try to perform the action you were trying to do and check if it now works.

You should delete the following folders if present:

• C:\Program Files\Mozilla Firefox
• C:\ProgramData\Mozilla Firefox
• C:\ProgramData\Mozilla
• C:\Users\username\AppData\Local\Mozilla
• C:\Users\username\AppData\Local\Mozilla Firefox
• C:\Users\username\AppData\Roaming\Mozilla
• C:\Users\username\AppData\Roaming\Mozilla Firefox

Also cleanup your temporary and rubbish files with Windows built-in hard disk cleaner or alternatives such as CCleaner or TuneUP utilities.

Did this solve your problems? Please report back us!

If you can't remove the Firefox program folder (C:\Program Files\Mozilla Firefox\ or C:\Program Files (x86)\Mozilla Firefox\) then see if you can take ownership of that folder if you can't change the permissions.

By starting Windows in 'Safe Mode' I was finally able to delete the Mozilla folders that remained after the uninstall.

Thank you very much for your help in resolving this.