Connecting a PC in the bedroom to the reciever in the living room, - cheap.

What’s the best and cheapest way to get the MP3’s from the PC in the computer room to the living room’s entertainment center?
Is there a fairly inexpensive way to do this wirelessly?
What would you recommend if it were your system?

The reason I ask, is my old man just got a new computer and he has a really awesome sound system in the living room. Need to get him hooked up so he can play any MP3s on the PC through the entertainment system, probably about 75 feet apart.
Ranch home with basement and a wireless router already in place.

If it were me, I’d go with a wireless solution, like this, for example. You can probably find similar products for a lower price, if $40 is too much for your budget.

Something like that would be perfect. I had in mind that I’d need about $100 to accomplish this so $40 is good news.