How do I stop automatic snapshot creation in 6?

I could configure older versions of Parallels Desktop never to take or delete a snapshot unless I told it to.

I can't find this option in version 6. I just lost a half hour of work time because while I was out of the room PD started deleting snapshots and I couldn't cancel the process or even force quit the program.

How do I configure PD to take or delete snapshots only when told to?

Thanks for any help.