1. Your computer shouldn't turn off by itself. This is probably caused by the CPU overheating (if it works 100 %). But the main cause it's CPU cooler wich probably wasn't cleaned up since ages and can't do his job properly.
2. 3000+ Barton CPU should play with no problems 720p and 1080i. I am using (and I reccomend) for MPEG2 files Elecard MPEG2 decoder and for x264 CoreAVC decoder.
3. Settings:
a) if you have .TS files, transform them into regular MPEG2 files using HDTV2MPEG2
http://download.videohelp.com/downlo...2_v1.11.89.zip No quality loss, takes a few seconds to transform.
b) when playing an x264 file, open CoreAVC properties (rightclick->options->filters) and set deinterlacing to "no deinterlacing" and deblocking to "skip all deblocking".
This settings will reduce the presure from your CPU.