I need some info on how and what guidelines I need to stay in to upgrade my cpu, currently I have pavillion 750c that has a 1.8GHz 400MHz FSB (williamette) 256K L2 cache, how much more can I increase the cpu also my motherborad is ASUS P4B266-LA, all the advice will greatly help, because I just bought 2.8GHz 400MHz (northwood) 512K, installed and nothing happend.