Several PCI cards can do
HD. I have a Broadlogic/Vbox ABA2030 that will handle them. You only need a PC that has a 2Ghz Pentium 4 or better to decode and display the picture, pretty common these days. The PC cards can also handle
AC3 sound, something a lot of STB units can't do and they are cheap on ebay. I only paid $25.00 for the 2030.