I suggest you read all of this post before doing anything, but the short answer is you reset the sync password as explained in this article: * [[I've lost my Firefox Sync account information - What to do]] But be warned that will cause irreversible loss of sync data (Do you have other devices synced ?) -------------- I'm not sure what you are trying to do and why, so a bit more information will help me understand. * Are you only trying to stop a dysfunctional sync process. * Did your ''dead'' computer have useful Firefox info on it that you would want to sync if it was working. How important is that information ? ** Trivial not worth trying to recover. -> Very important e.g. for work/studies. * When you say died I presume it is not functional, but do you have backup images of the hard disk or many folders/files, and do you still have the computer and its internal hard drive? ** is it a laptop or desktop pc, and roughly how old ? & how old is the current laptop? ** Do you remember the Firefox version on the old computer ? OR roughly when was the last time it was used and been likely that it would have updated Firefox ? I am wondering if it is worth the effort of trying to recover info, or whether all you want and need to do is just stop sync, and possibly start again if you have something else to sync with. There are sometimes manual methods of obtaining and transferring the data that sync updates, utilising just the old hard drive or suitable backup.