Can I run a computer using DC power?

Solution 1:

Google does exactly that! They do not have the UPS in the datacenter, they have the UPS on the machine itself, and feed DC to the mainboard. And they are only feeding 12V, as it is more energy efficient than lower voltages.

Solution 2:

Make sure you take a look at Mini-box.com's selection of DC-DC ATX PSUs.

EDIT: I see that your original link is from there! :-) I will actually be buying one of these this summer, as I notice that their selection has increased to include some ranged input voltage PSUs. Look at the M4 enclosure for mounting in a more traditional style. Then, you can run wires direct to your box. Visit your local hardware store for some good insulated options. Or, hack a cable to a power supply that you don't use any more, etc.