I was trying to do the same thing, and went down the external USB video card route and never got it to work. I've ended up using a cheap Nettop machine and the keyboard/mouse sharing solution Synergy. I have the feel of one machine, but it's distributed (I use the nettop as an auxilary/utility machine for browsing, printing labels, etc.... The Acer Revo AR1600 can be had for about $100US on ebay and is a nice little machine that takes up very little space.