Yeah the diff is easy And back offtopic hehe Bus speed is controled by the mother board via jumper settings windows has no limits on bus speed on the CPU If that was the case people would not use the OS on a P4. Hey I even used windows 95 on my P4 2 gig If you have to leave the case off then I suggest you check your CPU fan for dust. Maybe get a bigger heatsink and fan. Oh yeah right now I have a AMD K6-2 550mhz CPU and heatsink plus fan sitting on my desk do you want it ? Windows Xp runs with 256mb.