Do you have the recovery key you were given when you created your Sync account?

Please note that Sync is NOT a backup tool and should never be used as such. ALWAYS make a hard copy of your Firefox data before doing anything like a Windows reinstall.

I'm afraid I don't have a recovery key. I had years of bookmarks and stuff there, it would be extremely devastating to lose all that.

In that case, no, it cannot be recovered. If you had a backup of your profile we could help you import that but you apparently do not. So unfortunately that information is gone.

Didn't you backup any personal data before installing Windows 8?

• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

I do have my whole C:\Users\'myusername' folder backed up. Does that help with anything?

Yes it does. You can probably recovery your profile from there (keep in mind it is a hidden folder, so enable hidden files and folders) Recovering important data from an old profile

Oh my god it worked!!! Thank you so much, this is very important to me!! Is there any way I can recover my last session from that profile folder as well?

You would need to copy the sessionstore.js from that profile to the current Firefox Profile Folder to get that last session.

• http://kb.mozillazine.org/sessionstore.js