windows come with remote desktop, you set that up once, and they you can just log in to it.
render farm software should start up automatically, there is a "Startup" folder in windows, you can just throw shortcuts of things you want to open on boot into there.
the problem with microsofts remote desktop software, is it doesn't activate any dedicated video cards, it has its own drivers, so openGL/CUDA don't work. For stuff like that you can use "Team viewer" free software, or a VNC client/server deal.