What would cause a loud humming sound to come from surround sound speakers when connected to a computer?

Could be that your speakers are too close together or if you are using a boom mic or other mic it may be too close to a speaker. A power transformer/converter could cause that too if it is too close to a speaker. This humming is a ground loop. To get rid of this there are a few options. If the computer is plugged into the surround sound through a stereo mini to two rca cable you might try replacing the cable. Another option is to go over to your local radio shack and pick up an RCA ground loop eliminator. RCA is not the name brand but the cable type. It is about $15 and it looks like a D battery wrapped in black plastic with two rca cables coming out of either end. You will also need some couplers to attach the stereo mini to rca adapter to the ground loop eliminator. It is expensive but it will work. If it does not eliminate your hum radio shack will take them back with the packaging and reciept. (also if it doesn't work one way try flipping the ground loop eliminator around the other way.)