1) From your PDA if APDL is running, click "Options" and "Exit" to end the program.
2) Using the "Explore" button on ActiveSync on your PC, navigate to your PDA's "My Documents\APDL" folder.
3) Copy the contents of "C:\program files\airlinelogbook.com\[8 digit pocket pc id]\apdl\backup" to your PDA's "My Documents\APDL" folder.
4) Restart APDL, all data from the backup will be restored.
As to why your data was lost ? We store the data in the "My Documents" folder so it is not associated with the application. Removing an application will not remove the data. However, Loss of Backup Battery, Hard Reset, or Restore from a backup prior to APDL will remove the "My Documents\APDL" folder.
Running APDL SingleSync will create a backup to your c:\program files\airlinelogbook.com folder. Routine backups of this folders are recommend for long-term backups of your APDL data.