Can turning a mac onto it's side, (so that the height is longer than the width), be harmful to the computer?

FWIW, I’ve been turning my Dell on its side to watch movies in bed for a long time, and it’s still ticking after more than 3 years.

It won’t damage the computer, as long as you don’t block any air vents. Also, don’t move it while it is on and the hard drive is spinning, unless you have a MacBook (Pro), in which case the motion sensor will lock the drive while it is in motion.

Thanks for the answers guys, I’ve been hearing some loud noises from the fan, but I’m going to get a seperate monitor anyway. I’m working on building an arcade machine from an old computer, and I’ll probably just get a rotating monitor for the display.