Just let it render overnigte as carteron suggested. You can stop the render if you need to use the computer and save what you've done so far, then reload it later and restart the render (provided you haven't made any changes), and it will pick up where it left off. With a P3/700 and 128 MB RAM, the longest render I've had lately is around 8 hours, that was because I had more lights than I normally use and objects with high polygon counts. I general I see about 40 minutes to a couple hours for an average render. TL