Ask about Thunderbird here; https://support.mozilla.org/en-US/products/thunderbird

As of Firefox 53 in March 2017, WinXP and Vista won't be supported any longer. http://www.ghacks.net/2016/09/27/firefox-53-no-support-for-windows-xp-or-vista/

https://support.mozilla.org/en-US/kb/end-support-windows-xp-and-vista?cache=no +++++++++++++++++++++++++++++++++++++++ https://support.mozilla.org/en-US/kb/install-older-version-of-firefox?cache=no Be sure to read everything here.

If you still want to downgrade, look under; I still want to downgrade. Click the Directory of other versions and languages link. Look for the directory of the version that you want. But, remember that old versions may have security issues.

You should also check out Firefox; Extended Support Release {web link} ESR Notes System Requirements

Use the above links to download the Firefox version you want. Save the file. Then Close Firefox.

Let’s do a full clean re-install;

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86)

Mac: Open the "Applications" folder. https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac

Linux: Check your user manual. If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it. See Install Firefox on Linux; https://support.mozilla.org/en-US/kb/install-firefox-linux

If you downloaded and installed the binary package from the Firefox download page, simply remove the folder Firefox in your home directory. http://www.mozilla.org/firefox#desktop ++++++++++++++++++++++++++++ Do Not remove the profiles folder.

Look for, and rename any Mozilla or Firefox program folders by adding .old to them. Do not rename the Mozilla Thunderbird folder if there is one.

After rebooting the computer, run a registry scanner if you have one. Then run the installer. If all goes well, remove the OLD folders when you are done. +++++++++++++++++++++++++++ If there is a problem, start your Computer in safe mode and try again.

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode This shows how to Start all Computers in Safe Mode; Free Online Encyclopedia

This did not work. I tried installing a 4 series firefox, and it told me I needed win 7. I have never seen that before. I did get a 2 series to install, but none of my history/bookmarks installed. Thunderbird still crashed. While trying to install a different version of ff, it created an old firefox data on my desk top. Would running checkdisc help?

Dos CHKDSK Checks a disk and displays a status report.

Go ahead if you want.

The old Firefox folder on the desktop contains your original profile data. Just let it alone for now.

Chkdsk did not help. I am going to try and restore a complete back up.

You need the Firefox 52 ESR version for Windows XP.

Firefox 52.3.0 ESR:

• https://www.mozilla.org/en-US/firefox/organizations/all/
• https://www.mozilla.org/en-US/firefox/52.3.0/releasenotes/
• https://www.mozilla.org/en-US/firefox/52.3.0/system-requirements/