Thank you for the links. I couldn't backup the profile on windows 8.1 since that operating system is no longer accessible from my now upgraded windows 10 environment. I should have backup the firefox data using it's tools but I did not. The upgrade copied my old windows 8.1 files to a folder windows.old. So I first deleted the contents of the profile folders on my windows 10 machine. Then I moved the contents of two windows 8.1 profiles, one user\appdata\roaming\mozilla\firefox\profiles\and (Copied the windows.old )profile contents The other was user\appdata\local\mozilla\firefox\profiles\and (Copied the windows.old )profile contents When I removed and re-installed firefox, the install failed and I received the message 'the firefox profile cannot be loaded, it may be missing or inaccessible'. I found this document: https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible#w_profile-was-moved-or-renamed It suggested trying to rename the profile members to their prior names, so I looked at the prior names of the profiles I had deleted that were in the recycle bin and renamed the profile folders to that name and re-installed firefox and now firefox looks the same as my old windows 8.1 firefox used to. Bookmarks, extensions are all back. Thanks a lot for pointing me to the links that got me started. This does prove to me that the profiles can be copied outside of the firefox backup program if that wasn't done, but I will in the future take the easier route and be sure to use firefox to create a backup. Thanks again, Doug