Hi MikeA few questions: Your 333 config was stable? You exchanged the 333 to 400mhz-modules all at once? At that point your RAM settings in the BIOS were still set to your personal settings? If the answer is yes 3x, it could be related to 'deep' RAM-BIOS settings. A possible workaround is, to boot your PC with one of your 'old' modules. Go into the BIOS and set RAM settings back to 'controlled SPD,' make it nice and 'conservative' again to then let the comp reboot. Go into safe mode or whatever to turn your computer off asap (without having to stress the power button). Unplug..!! Put your new modules in again. Plug in... Boot... Hope for the best... Let it boot to windows once before you restart to do BIOS tweaking. Have a flight at standard settings, test it a little. Only up voltages very cautiously, 2.8V sounds like a lot. If, it's better to also get a nice, cool case. In case, also buy the best power supply available. Another way is to put the RAM-modules in one by one. This way, it's also great to see your machine become a rocket, once dual channel gets enabled. Just a few ideas..Kind regards Jaap

Mike,If your CPU/RAM ratio is 1:1 and you are overclocking the CPU internal clock from 200Mhz to 250Mhz, then your CPU is running at 12 x 250Mhz = 3.0Ghz. I've heard that the 2.4C P4 is a very good overclocker, but not all CPU core samples are equally good. At 250Mhz, your FSB is overclocked to 250Mhz x 4 = 1Ghz. Your RAM would be at 250Mhz x 2 = 500Mhz, so I don't understand your question. You already are running your memory at 500Mhz if you are using the 1:1 ratio in your BIOS.If you are not and can't POST at 1:1 and at 250Mhz CPU clock, then perhaps you might need more cooling in your case and/or for the North bridge chip and CPU on your motherboard. Also, you might need a bigger power supply (you did not provide full specs of your rig). Other than that, the problem could simply be your sample CPU or the memory module itself.Good luck,David