My friend has just purchased a HD TV. We wants to upgrade his PC to a specification that will play 720p HD .mkv files smoothly. I can plug my laptop into the screen and play movies in high definition no problem. My spec is a AMD 1.6 Dual core, 256 ATI shared Graphics and 1256mb of free RAM (not being used by shared graphics card). His PC is fairly old put has 1256mb of ram an ATI 125mb Radeon 9250 and unfortunately a Celeron Processor (not sure of clock speed). Depending on the socket that the Processor sits in if we can upgrade this to a Pentium 4 3ghz do you think the PC’s specification will be high enough to run the HD video. I have purchased Core AVC and also use the combined community codec pack so will probably use the same on his. Any suggestions or advice would be much appreciated. Cheers all.