Digital Out Dell 1525 To DAC Section Cary 303-200

I am having a problem running into the DAC section of my Cary CD player. I went thru the menu for "digital sound" on the P.C., hooked up the digital via a special 7 pin S Video/Audio Adapter and S/PDIF Cable into my Cary. I am getting sound thru the speakers but every so often I get a popping sound and a louder version of what I am listening to. The output from the computer is registering on the DAC. Unless you have a Dell you may not not understand digital sound coming from a S Video plug (normal = 4 pin I have 7). Any thought would be appreciated.
I would avoid Dell computers. I have had nothing but problems with them trying to stream audio data from USB.
You have probably sorted this out by now. If not, for what it's worth I output via usb (using ASIO4ALL driver/winamp) to a Trends UD-10 transport, optical out to my Citypulse DAC and have had zero problems. If you're still struggling you might look at the Trends or similar USB converter.