Replying to Vegas 9 Rendering Issue

I am editing on a two day old computer. I don't know much about computer specifics, but it has 4tb of hard disk and 8gb of ram? Anyways, its a really nice computer. Editing goes fine, but as soon as I start a render in .wmv I get an error message saying that the system is low on memory, and the problem could be fixed by closing other applications. There is nothing else open. When I render to .avi, I get a 2.8 gig file for a 20 second 720 60p clip. The rendering works, the file is just much much too large

Any idea what I should do to either make .wmv work or reduce the .avi file size?