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After the update last night, Mozilla was "not a valid windows (something)" No access to internet. Restore points Deleted.

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A I tried to get to the internet the message that firefox was installing an update and would start momentarily. Never started and when I tried to get on the internet an error message came up that said Mozilla was not a valid windows (something) and I needed to check the install disk. I had no internet access. I tried to restore to an earlier date and the restore points were deleted and the only month shown was June. This is my computer at work

A I tried to get to the internet the message that firefox was installing an update and would start momentarily. Never started and when I tried to get on the internet an error message came up that said Mozilla was not a valid windows (something) and I needed to check the install disk. I had no internet access. I tried to restore to an earlier date and the restore points were deleted and the only month shown was June. This is my computer at work

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If there are problems with updating then best is to download the full version and uninstall the currently installed version.

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

  • Uninstall your current Firefox version.
  • Do not remove personal data when you uninstall the current version.

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.

Your bookmarks and other profile data are stored elsewhere in the Firefox Profile Folder and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox.

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That is what I did. But i deleted everything first then downloaded a new install.

Thanks for your help

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If you get corrupted files while downloading then you may have Anti-virus software that is interfering and is causing problems.
In that case you can try to disable live (real-time) scanning in your AV software.