How can I connect my TV and PC to one set of surround sound speakers?

SIMPLE SOLUTION, BUY A CORD, WAL MART OR RADIOSHACK SELLS THEM FOR UNDER 5.00. THE PLUG PLUGS INTO YOUR AUDIO OUT ON PC, WHICH IS HEADPHONE JACK, THEN CONVERTS TO RIGHT AND LEFT COMPONENT JACKS TO PLUG INTO THE BACK OF YOUR RECEIVER. VERY SIMPLE WORKS EXCELLENT, I DO IT WITH MY LAPTOP AND DESKTOP.

I am assuming that you want to use all the speakers in a surround setup instead of just the left and the right speakers. What you will need is three of the cables that the other responses talk about (the three little plugs on the back of the computer each support 2 speakers--green is front left/right, blue is rear left/right, and red is center channel/sub, just make sure that you configure your soundcard to output that way!), or you can get a sound card for your computer that has some sort of digital output(either digital or coaxial) that you would hook up to the receiver, which in turn would be hooked up to the TV

what happens if you use your tv and pc at the same time, it will overload your speakers and confuse the system

Shark is right, your going to need to plug get a 3.5mm plug to a 2 rca plugs and then you just plug the RCA's into the back of your reciever. You will have to change the input on your receiver when you want to switch between sound from your TV and PC, but you won't have to change any cords around.