Power

today i just reformatted my computer back to windows vista...windows vista are so laggy on my computer even i have a 1GB ram and a dual-core processor but it still lag...so i changed it to XP...XP is much more smoother as compared to vista when running on that performance rate...but the disadvantages was that when ever i play a game ,it will restart my computer...so i change back t vista..and it will not..think is overheat or software problems...but i'm currently still researching on why it happen....if u know..pls share with mi