The first thing to do is check which protocols are implemented on your receiver. That's almost certainly DLNA, although there are others. Then you need to set up your PC as a server using that protocol. Recent versions of Windows Media are DLNA compliant, I think, and there are also a number of third party software packages available (including free/shareware). Make the software point to, and share, the folders containing your music files. Your receiver should then "see" those folders.
At least in theory, it's as simple as that. Practically, maybe, maybe not. My NAS was no problem, but with the PC it was slightly trickier (I had to assign a fixed IP address to the receiver and change a Windows network setting). Shoot me a PM if you have trouble. I am not an expert, by any means, but maybe I can help...