Computers and plants sure don't seem like they'd mix very well, but that just shows what I know. This plant/computer hybrid concept manages to be a functioning computer and a functioning plant at the same time. It's mind-boggling.
This concept, called "Secondary Growth," is essentially just a planter that happens to have a computer built around it. The bits filled with soil are kept more or less separate from the bits filled with delicate computer equipment, and otherwise, you just plug it into the wall, fertilize as normal, and watch it grow. Apparently, it creates "an interesting contrast between a constantly changing organism and an unchanging object of permanence." Er, okay then.
Whether or not you buy the whole integrated plant thing, one brilliant feature about the computer itself is that the graphics card, hard drive, RAM, and processor are all in cartridges that are easily swappable. And the fact that they stick out of the computer like they do makes them easier to cool. If it's cooling you're worried about, though, just water the plant, and presto, you've got a water-cooled PC.