You have to be REALLY CAREFUL about the RAM configuration because if you fuck it up, or put in a number higher than your actual RAM, you will kill Vegas.
Yes, this does work for Vegas 8.0 to 12.0 as far as I know. I'm using 9.0 in this tutorial.
(sorry about the screaming children in the background, our neighbourhood is currently having a community bitching about something that just happened on our street outside)
Easy copy-paste of the RAM settings:
you hold down shift as you go to options and hit preferences. let go of shift. find the "INTERNAL" tab and search with the bottom bar for memory. then you gotta figure out how much RAM you have in MB. not GB. and put that into the tab that says "memory needed by vegas (MB)" under value. this is the RAM list:
(THE COMMA IS IMPORTANT.)
2 GB = 2,048
3 GB = 3,072
4 GB = 4,096
6 GB = 6,144
8 GB = 8,192
12 GB = 12,288
16 GB = 16,384
you gotta render on preview - full (make sure both the preview window and the actual render settings say Preview) and make sure you're rendering as wmv, 3.0 mbps or 4.8 mbps, 1280x720, 12.5000 fps, 20 keyframes per second, set the sharpness to smoothest, and your audio to 96 kbps