I'm thinking about setting up a DC, Exchange, file- and webserver at home, but at the same time the computer that has to be used shouldn't be noisy or very power consuming. I was thinking about maybe using Hyper-V Server or alike to virtualize these servers.
Maybe this should be an Intel Atom, or maybe something else? Any ideas or alike for me to use in the further hunting for some cheap hardware?
Craigslist has some cheap servers, but not energy efficient. The old amd 940 opterons use 55 watts and go for less than $10 at some venders. The boards were being closed out at computer geeks for around $24 shipped for awhile, but they sold out. Make someone an offer and you might get a bargain, but it won't be low energy. Some of the fancy dual core atoms with board go for almost $200, so figure the initial investment versus energy cost savings if you can.
Newegg has a big tyan 4 cpu true server board that takes quad core socket 1207 amd cpus for only $43 shipped (open box); it will sell out in minutes. This board requires a special case; it won't fit in a standard atx case. The 1207 opteron quads start at $45 at starmicro. They run at 1700 hertz or higher and use about 55-75 watts.