I decided my Jornada 420 is too unreliable and slow to keep using it and want to transfer all my data back to my E-100 which never has any problems.
To prevent old items already previously synced the Outlook on the desktop from being mixed with actual items on the Jornada, I deleted all Tasks and appointments on the desktop and then set ActiveSync to "Always replace data on the desktop", what I failed to notice is that this rule applies only to items that are in conflict, not all items, so this resulted in it wiping my Jornada clear of all data instead of transferring all the Jornada data to my desktop. I knew there would be such a risk (thought I never expected something this disastrous) so I had backed up the 420 to a CF card and was able to restore everything.
Now my question is, how can I ever sync my 420 to the desktop again without it deleting everything on the 420 as I did on the desktop? I basically want to transfer all Tasks and Appointments from my 420 to my E-100, I had no problem doing it the other way around but that time I hadn't deleted everything in Outlook first.
That's what I always do. It's relatively painless. If there's an ActiveSync backup file for that device, you can always move the backup.stg file to another location before deleting the partnership.