I think it's just best to get into the practice of saving very frequently (every few minutes), and also to save new copies of your file every so often just in case something goes wrong with your only copy!!

I personally find autosaves in other programs are a bit annoying as they tend to save right when you're doing something and cause it to lag for a sec...

So, get in the habit of saving often... it's a good habit to have

Edit: there might be something in the temp directory on C:... maybe. I know maya uses it for some things... worth a check.