I have Vegas 5, though I don't use it much, and the 'help' under 'Index' then 'Backup' says there is an automatic backup, every 5 minutes, but you need to make sure it is switched on. Go to 'options' then 'preferences', then under the 'general' tab there is a long list of items you can tick or not. The backup is towards the bottom. I haven't seen a way of shortening the time between backups.
Win XP, Athlon 1.8, G force 3 T, 1 60gig drive + 1 250 gig, Pinnacle Studio 9 plus mostly, Premiere 6, and Vegas 5 sometimes, Soundforge, Cool Edit.