I've encountered this extremely strange problem with my computer. Everytime after I choose "Turn Off" from Windows XP Pro SP2, the Windows will shut down properly and after that if I press the power button, my computer won't boot. If I choose "Restart" from Windows, the Windows will shut down and then when it try to restart, it just won't boot up. All the fans (CPU, VGA, North bridge) are functioning properly and both the red LED1 (5VSB) and yellow LED2 (VCC) lights up normally. However, the PC speaker doesn't beep and the monitor will still be in standby mode (no POST screen shown).
All I need to do is to reset the bios. Then when I power up again, it'll tell me that the CPU has been changed, press F1 to continue or ESC to enter setup. If I press F1, the Windows will boot properly. If I enter setup, and then "Quit without saving", it will also boot properly. But if I enter setup, did not make any changes, just choose "Save and exit", it will not boot!!!!
My hardware specs are below in the signature. The problem must be in either the mobo or the CPU but I don't know which one or how to find out. I've tried different VGA cards (from the early Geforce 6600, to ATI X850XT, and the latest Geforce 7900GT), different power supply (from the original CoolerMaster eXtreme Power 430W to the current Antec TP II 550W) and different DDR RAMs, but it is still the same. The mobo bios is the latest kn819 version downloaded from abit website.
My CPU is AMD Athlon 64 - AMD Engineering Sample 00 (ES) with default clock at 4*200MHz = 800MHz and default CPU voltage at 1.1V. When I boot into Windows by resetting the bios, I can actually overclock it using clockgen to 12*200MHz = 2400MHz @ 1.4V and it will run stabily (http://valid.x86-secret.com/show_oc.php?id=115780). Too bad I can't get another CPU to test the mobo.
Any ideas???? Please provide your opinions, thanks in advanced.