Logic tells me that a 1080i broadcast requires more effort to process than one in 720p yet programmes from TV3 are smooth as the baby's posterior. TV 1 & 2 are more like mine.
I tried enabling the EVR in Media Portal but it threw the machine into a 100% CPU spiral of death so switched back.
Oh the pain and trauma.
@seasport do let us know if a Vista install resolved the problem. Much as I hate the idea of paying for another MS license.