So you're telling me you have to have a GOOD computer to make stuff in Sony Vegas?
forget me...
Well, not REALLY. But if your computer sucks balls then don't expect it to run nicely. Don't forget you have to render videos once you're done which takes some time depending on the video and your computer. For me it takes maybe a minute to render a 30 second 720p video, with a Core i7 930 @ 2.8 GHz, 6GB RAM and a GTX460.
I'd say you need at least a high-end dual core, 4GB RAM, and a mid-tier GPU.