A lot depends on the number of layers on the system board and if it has a ground plane. I know I never had a problem with AM radio on my desk at work and I had 2 IBM PS/2s running in my office 24/7 one in a wood case. http://esteroriverheights.com/electrical/woody.jpg Some lesser "clones" would affect my radio whenever they were on in the shop around the corner from me (covers on helped a little).
