What are you capturing the files with? FRAPS? If so, just drop the FRAPS avi's on the Vegas timeline, make any edits you want and then select File > Render As.... In the Render As dialog under Save as type: select Video for Windows (*.avi). Then under Template: select the render template you want to use. If your final format is DivX you’ll have to make up a custom template that uses that codec using the Custom button..