If you have a TV tuner card in your PC, you can stream for free, though you would need something like the Snapstream setup to change channels. PPCT has a thread on how to set Windows Media Encoder to stream to your PPC
here.
I have a Hauppauge WinTV and use WME to stream live TV to my PPC via wifi.
The same setup can be used to stream music from your hard drive, but mapping the drive as local with Resco Explorer would be a better way to go, since you could access the music directly, rather than re-encoding it.