Have you looked into replacing the CPU? I'm guessing since it's an Epia board (from that link) that it's got a VIA C3, which isn't really enough for any MPEG viewing...but I also think you might have a standard Socket 370 that may be able to handle a Tualatin PIII, which would have a much better time with your video decoding.
Otherwise, I can highly recommend the Biostar ideq 210V, which has onboard video, sound, 100mbit LAN, and USB (and retails on Newegg for only $150) and an Athlon XP or Sempron (Socket A).
I do not understand what I do. For what I want to do, I do not do. But what I hate, I do.