Crowdsourcing the Lazyweb

I need a PC. Minimum specs are 2GB RAM (although I'd prefer 4) and 1.6Ghz. I need to have dual monitor setup, so it needs 2 video cards or at least a slot for a second one. I'd like it to be small (and more importantly light) as possible because it is part of a portable system and the easier to carry and set up, the better. I don't think a laptop will work because I  need dual monitors and I don't think laptops can support 3. Too bad because I have a netbook that totally would work. Anyway, I'm probably looking at grabbing something off of craigslist, even the super cheap ones have everything I need.

I had one that would have worked but I gave it away just recently, I hadn't used it in EVER and it seemed like the right thing to do. I used to be really good at this stuff, building computers from old parts, but now the options are so stunning, I don't even know where to start. 

Mac Mini would possibly work except My software is Windows. 
Can someone tell me where to start or possibly what to avoid?