Did they verify what OS bit was your OS? This is something that needs to be verified? 32bit system can't use more the 3.5G RAM but 64bit can go high as it wants. So did you make sure the shop was not just selling RAM if your system was only 32bit system? Your DLL file shows it as 32bit so that can't be a RAM if that is the case. You could also have bad RAM chips as well. To do a Firefox backup you need to follow the Firefox FAQ on backup and importing to insure the data gets saved and transfer correctly. You can't just copy folders that will corrupt Firefox itself. Some how you need to get the drive hookup and working in the OS it was installed on and do the Firefox FAQ backup to a USB drive and then use the new setup to migrate them back. Could be more then this but it's a start. If not do a search online for Firefox backups that you need and you should get links on how to find or see what to do as well. https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them https://support.mozilla.org/bm/questions/1271699 https://support.mozilla.org/si/questions/1396640

The Old Firefox Data folder is only populated when you use the built-in Refresh/Reset/Tune-up feature. To find other recent profiles, try the steps in the first section of the following article: [[Recover lost or missing Bookmarks]] Are any useful profiles listed on that about:profiles page?