Was Linux installed on the old hard drive that crashed because since you mention C: being a SSD what would refer to Windows ? Were using Firefox on Windows as that would likely have the profile folder on the SSD C: drive or were you using Firefox in Linux ?

Firefox uses two locations for the Firefox profile folder ?

Location used for the main profile that keeps your personal data (Root Directory on about:profiles).

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\<profile>
• ~/.mozilla/firefox/

"AppData" (XP: Application Data; Mac: ~/Library; Linux: ~/.mozilla) is a hidden folder.

You can copy certain files with Firefox closed to the current profile folder to transfer or recover personal data.

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (encrypted logins;32+) and key4.db (decryption key;58+) for Passwords saved in the Password Manager
  key3.db support ended in 73+; to use key3.db in 58-72, make sure to remove key4.db
• cert9.db (58+) for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words added to the spell checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

Probably you'll use a USB caddy or some other method to access the old drive from your new Windows installation? To facilitate exploring AppData folders, you can set Windows to show hidden files and folders:

https://support.microsoft.com/en-us/windows/show-hidden-files-0320fe58-0117-fd59-6851-9b7f9840fdb2

In the sessionstore-backups folder, the recovery.jsonlz4 generally has the last state of your tabs before the crash. If the file is unrecoverable, recovery.baklz4 is the immediately previous state (about 15 seconds earlier). The other files might be needed if neither of those works.

Optional Session History Preview

I have a tool to extract out the compressed session history contents and display them as a list of tabs with clickable links. You can use that as a backup or workaround in the events that the file is readable but your new Firefox can't be persuaded to restore the file.

https://www.jeffersonscher.com/ffu/scrounger.html

Drag and drop the compressed file onto the box on the page and a script should show the contents. Typically they are standard typewriter characters (no weird symbols) starting with:

{"version":["sessionrestore",1],"windows":[{"tabs":[{"entries":[{"url":

Click Scrounge URLs to build the list and confirm that the data structure is intact. You can use Save List to archive an HTML file (local web page) with the list shown on screen.

Thanks for the replies. That from jsher2000 allowed me to recover my tabs, which I tend to use to remember information I want to revisit. Most helpful!

Now I have to figure out how to recover my Thunderbird stuff.

Now I have to figure out how to recover my Thunderbird stuff.

The relevant data path is:

C:\Users\username\AppData\Roaming\Thunderbird

But I'm not sure how best to reinstate the old data on your new drive. To get the best attention to this issue, please start a new question under Thunderbird:

https://support.mozilla.org/questions/new/thunderbird/form

Thanks! I've submitted a question to the Thunderbird forum.