Even a computer specialist could nt be answer all you question.
hundred and thousands kinds of computer hardwares and softwres in the world. which one do you prefer?
home computer? main frame or microchip or what?
software has os, application, special etc.
you can search on googls or any search engine.
if you are use personally, and hope to play game, try to select a mainboard support doublecore or quetarcore cpu. and a display card could be 7900, 20" lcd monitor. 200G disk/7500n. 1--2G RAM . OS can be windowxp or vista...enough.
wonderful to play game. my neighboor boy config such machine. only around 10K rmb (Chinese money)