Media Stuttering

In the last couple of months i have had a problem with both Audio and Video stuttering, starting from nothing but getting progressively worse and worse. Initially i thought it was some Spyware or virus lurking in the background but extensive searching and eventually a fresh install of Windows has not cured it. It seems to be related to the S-video out that i use to feed my standard analogue TV. If the video screen remains on the computer monitor there is no stuttering as soon as i move it over onto the secondary screen it starts. The video card is a AMD Radeon 7000 series and I have tried updating the drivers but that has not made a blind bit of difference. Please can anyone help i am close to putting the whole thing out of the window.