If the server is that unstable, you need a new one. If it's mission critical
that you cannot lose even an hour's data, you should consider using
SQL-Server for an engine instead of Jet. For Access to be backed up you can
write a simple batch file that runs ever hour (using the Windows scheduler).
You will need to kick everyone out because copying open files can lead to
data corruption. For a Kickem out routine, have a look at:
http://www.datastrat.com/Download/KickEm.zip
Instead of doing it manually, use a Timer event on a form to do it.
