There was an error launching the application

This error indicates that either Firefox is not installed or your shortcut to it is incorrect. Make sure that Firefox is installed at the location specified by the shortcut. If it isn't, install Firefox if necessary, then modify the shortcut to point to the correct location.

The program must close to allow a previous installation attempt to complete. Please restart.

(Windows 7 and Vista) If you are receiving the above error message while attempting to start Firefox, try to restart the program. If the problem persists, do the following:

1. Restart your computer.
2. Select the Start Menu in the Windows Taskbar.
3. In the Search box, enter the following:
   %APPDATA%
4. Press Enter.
5. From the Application Data folder, navigate to Local\VirtualStore\Program Files\Mozilla Firefox.
6. Delete the file xpicleanup.dat.
7. Restart Firefox.

(Windows XP)

1. Click on the Start button and select Search to open the Search Results window.
2. On the left side of the Search Results window, click on the All files and folders link.
3. Click to expand the More advanced options list.
4. Put a check mark next to Search system folders, Search hidden files and folders, and Search subfolders.
5. In the All or part of the file name field, type xpicleanup.dat.
6. Click Search to begin the search.
7. If any results are returned, delete them.
8. Restart Firefox.

Error opening file for writing...

If you receive the above error when launching Firefox on a Windows system, you may be required by Firefox to log in as an administrator. You can either reboot the computer or, if you have an administrator account, you can execute the program as an administrator.

1. Find the firefox.exe program file in the Firefox application folder on your system.
2. Right-click the icon.
   • (Windows XP) Select Run As.... Select The following user:. From the User name drop-down, select Administrator or another user that has administrator privileges. Enter the password required to log in to this account. Click OK.
   • (Windows 7 and Vista) Select Run As Administrator.... Complete a similar set of steps, as those listed above.
3. The Firefox application is started using the administrator Windows account. The user that was used to log in to Windows at startup is still the active one.

Firefox 3 will not start on OSX 10.3.9 or earlier

Firefox 3 will not start on Windows 98/ME or earlier

Mozilla has stopped supporting OSX 10.3.9Windows 98/ME and earlier in Firefox 3.0 and higher. None of these operating systems are supported by AppleMicrosoft (and have not been for quite some time) and have multiple vulnerabilities that will remain unpatched. As such, you have the following options:

1. You can switch to another operating system. This is the most secure option. If you don't want to pay for a new operating system, you can get any of a number of versions of Linux which can run Firefox 3+ and can run on older machines. This ensures you have a completely secure system and access to all the great new features in Firefox 3+.
2. You can continue to use Firefox 2 which you can get from: our FTP siteour FTP site. Just because the browser will no longer receive security updates doesn't mean it will simply stop working. You will be using unsupported software on an unsupported operating system which poses a significant security risk.

Firefox will not start on Linux

If you installed Firefox outside of your package manager, make sure that your system has the libraries listed in the system requirements.