How can I recover uninstalled personal preferences?
I installed firefox beta 4 when I already had 3.6. I didn't like the beta version so I uninstalled it but forgot to uncheck the delete personal preference option. I didn't mind because I thought that since I already have 3.6 installed, those information would be safe from any modification to 4.0 beta. Now when I open 3.6, it comes with all my personal preferences (plugins, bookmarks, etc) all deleted, and in a brand new browser. I really need to recover them, especially the bookmarks. please help.
When you selected that option it would have deleted all of your Firefox personal data, included data used by Firefox 3.6
If you create backups of your important data, to restore the bookmarks you can copy places.sqlite from the backup and place it in your profile folder.
If you do not create backups, you may be out of luck. You can try using a data recovery program such as Recuva. Try searching for files to undelete/recover with a name in the format bookmarks-yyyy-mm-dd.json, those files would originally have been inside the bookmarkbackups folder inside the profile folder. If you can undelete one of those files, use the restore procedure in the Restore bookmarks from backup or move them to another computer article to restore the bookmarks from that file.