After 6000+ posts you should know that this isn't really the proper forum for those questions.
That said, however, your TV probably has a method to cycle through your available inputs, so you could select the PC input, or the TV input, and even probably Picture-in-Picture.
If your surround sound is issuing from your PC, then I think in most instances you'll need your television signal to enter your PC first. I suppose if your cable/satellite/whatever tuner box has audio out you could run the video direct to the TV and the audio into your PC. At any rate your PC will need to be on in order to get sound out of it.