Do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox.

• (32 bit Windows) C:\Program Files\Mozilla Firefox\
• (64 bit Windows) C:\Program Files (x86)\Mozilla Firefox\
• http://kb.mozillazine.org/Installation_directory

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 18.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other profile data are stored in the Firefox Profile Folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

I should have been a bit more definitive. I have uninstalled FF, with the windows uninstaller, by manually cleaning the files and the registry of any mention of FF or Mozilla, and by running Revo uninstaller - always rebooting and checking to see if the files are indeed gone. (I have set windows file preferences to see all files, including system files.) I have run 4 AV/malware scanners and found nothing but a few tracking cookies. I download, from Mozilla.org, (http://download.cdn.mozilla.net/pub/mozilla.org/firefox/releases/18.0/win32/en-US/Firefox%20Setup%2018.0.exe) a fresh copy of the Firefox Setup 18.0.exe each time and install when logged in as an administrator and choose "Run as Administrator". I get the same result each time I try to open Firefox. Consistently does not open, gives the error: "C:\Program Files (x86)\Mozilla\firefox.exe Windows cannot access the specified device, path, or file. You may not have the appropriate permissions to access the item." This happens even when I run the .exe file from the x86 program directory. I have also attempted to run in XPsp3 compatibility mode to no avail, I make the following assumptions: The system is not infected I am doing clean installs There is no existing trace of FF on the system I get identical results on one other W7 64 bit Optiplex 990 system with an i7 processor and 16 GB or ram. I CAN run in windows safe mode with networking. I have no other software or hardware issues.

Did you check the permissions of the firefox.exe file?

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

cor-el, thank you for the reply. You suggest: Clean re install as mentioned I already tried that; Download a fresh copy to the desk top, already tried that; remove program folder, already tried that, even with Revo uninstaller and registry search; FF permissions, as mentioned above, I checked those, going as far as taking ownership; Windows safe mode, as stated above, it works in safe mode. Also as stated above, another W7 Professional 64 bit, on a Dell Optiplex 990 i7, 16GB ram has the same problem. Any other thoughts? I have not disabled UAC, that is next.

If the file is there and it works if you boot Windows in Safe mode then some software must be blocking access to the file.

You can use the Autoruns utility to see which software and services gets started.

• http://technet.microsoft.com/en-us/sysinternals/bb963902.aspx

Do a malware check with some malware scanning programs on the Windows computer.
You need to scan with all programs because each program detects different malware.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender: Home Page:
  http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• http://support.kaspersky.com/viruses/solutions?qid=208280684

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

I am a network admin, so like I said above one of the first things I do in cases like this is is run a suite of AV checkers and a root kit reveler, nothing found but a couple of tracking cookies.

Finally have it running. Seems the enterprise version of McAfee was blocking the program install. Uninstalled McAfee, reinstalled Firefox, installed McAfee and it is now good to go.