There is a lot of discussion on the Internet about putting one of these crystal HD cards in to intel mac mins, so i was wondering, if i bought one, would I be able to put it in my PPC version to play HD files?
I am pretty sure the G4 Mac Minis don't have a slot for a mini-PCIE card. To the best of my knowledge the only PPC macs that could conceivably use a Crystal HD card are the dual core G5s (and only then by using an adapter).
look in the FAQ at the top of this page by Skinnezho. There is a link there. It's software, optimized for the G4. My ibook 1.25ghz (may she rest in peace) had no problem with 720p files. Couldn't do anything else, processor was pegged at 90%, but it played. Smooth.