Some people at Go Firefox! have reported some issues when attempting to upgrade from Firefox 3.6.16 to Firefox 4 on Windows. A couple I have seen include:
- Error 0x00000004 in firefox.exe
- Reboot required to complete update. User get this message when attempting to launch or uninstall Firefox via Windows Control Panel.
In both cases firefox.exe or one of it components got corrupted during the update. To fix this issue follow these steps to manually remove the damaged Firefox and to install fresh:
- Got to getfirefox.com and download (do not run) Firefox 4
- Close Firefox
- Locate your Firefox install folder. Default locations:
- Windows 32-Bit — C:\Program Files\Mozilla Firefox\
- Windows 64-Bit — C:\Program Files (x86)\Mozilla Firefox\
- Delete this folder and all sub folders. Note: your profile is stored elsewhere and will remain intact.
- Run the Firefox 4 installer downloaded in Step 1
Once the clean install is completed you should be able to run Firefox 4 with no issues.