EM radiation is not ionizing, and is VERY likely to be benign, especially with the low levels that the PC outputs. My advice on staying away from radiation sources:
avoid sunlight - many kinds of radiation there, some of which are proven to cause cancer
avoid concrete
avoid TV's and CRT's in general
avoid power bricks/wall wart power supplies
don't get too close to flourescent lights
Moral of the story - I wouldn't worry about the little bit of non-ionizing radiation that computers produce. There still aren't any conclusive studies to say that these fields pose a health risk.