I installed a version of firefox ""xDark™ Firefox Killer 8.0 (en-US)"". After this installation all my data was lost (and passwords) and I did not backup my profile before installation .Sync did not restore my passwords

When you download and install an '''''altered''''' copy of Firefox you are on your own or you are totally dependent on the developer of that altered copy for support. The only site from which to get an authorized release is the Mozilla site. The product that you mentioned seems to be available mostly on torrent sites. Good luck with anything that you get from those sites; anything on a torrent site can very easily be altered to install all sorts of malware on your system. You can try to un-install that altered copy. Try to locate and backup (before uninstalling the altered Firefox) your original Firefox profile if it is still on your hard drive. Then download, SAVE, and install the official Firefox. *See --> http://support.mozilla.com/en-US/kb/Backing+up+your+information *Official Firefox download --> https://www.mozilla.org/en-US/firefox/all.html '''If this reply solves your problem, please click "Solved It" next to this reply when <u>signed-in</u> to the forum.'''