Are your processor support HT tecnology??
Only processor with HT function will not lag in gaming and also sometime dual core processor support high speed.AND ofcuz you must have a good graphic card and enough RAm to run the game...But i think till now even windows XP are widely used, but it also lag
sometime when the computer was processing a huge
data.BUt i think windows 98 are good in gaming cuz it will not lag as long as ur computer met the requirement
of the game.....ANd also ur computer muz overclock properly.....IF not watever wat good stuff u put in, it will still lag.