michaeljc70,

Is this a PC assembled from parts, or a name brand system?

If it is from parts, look at the brand of the motherboard. Go to the motherboard manufacturers website, and look for a spdif output module. Many manufacturers offer this as an add on. If you have the manual that came with the motherboard, it will tell you in the section that covers the various headers on the board if a header for connecting the spdif is present on the motherboard you have. With this, everything you're sending from the PC is digital, so power supply, hdd noise won't be a problem. With spdif you can't even have noise induced on the ground to the amp/receiver, as the connection is optical!

If it is a name brand, take a look at the chipset. Is it a Creative Labs sound solution on the motherboard? If it is, then either it was poorly implemented, or you may have a compromized ground. Go through the normal steps to troubleshoot a ground loop... make sure all components are on the same circuit, all line cords designed for 3 prong plugs have ground intact, ground at the outlet is present.

If the sound solution is a generic one, if you get away from using any of the analog in the solution, you'll likely be fine. Try the digital coax or spdif output. If this is still a problem, try a sound card. Best Buy, Circuit City, wherever you can get a good quality Creative sound card inexpensively. Try it. If it doesn't do what you need, return it to the store!

Note that if you have to pay much for the Sound Card, it may be easier to just buy a stand alone music server.

In my opinion the issue in any of these solutions is not the quality of the audio, this is controlled by the devices chosen, and the rate at which the music is ripped. These variables are very controllable, and most of the solutions properly implemented will give good results. The real issue is the user interface! For whole house audio, how many locations do you need to control from? How many audio streams will you support? These are what really determine which solution you choose!