Mike Schropp's "BioComputer" is a PC casemod that actually grows wheatgrass, using waste-heat from the computer to provide a hospitable hothouse environment. He's posted detailed build-logs from the project, and plans more ambitious horticulture.
I can’t exactly recall when the idea came to me, but at some point I started wanting to use the heat from a computer as a way to warm the soil and help with germination/growth. I’m about as far from a botanist as it comes, I did some reading online and became pretty interested in the effects of soil temperature on germination/growth. I read different studies and papers from various universities. It was not too long into that process that I became hooked on the idea of using computer heat as a way to control the soil temperature of some sort of living plant life.
As the idea developed further I started looking into wheatgrass as a plant option. There is something clean and natural about the look and idea of a piece of grass growing in my basement. I thought the look would alter the space a little bit and add a bit of color along with something more than just metals and plastics. After reading enough studies and papers on the effects of soil temperature and germination with wheatgrass I felt like I had a good enough handle on the basics to tackle this.