i have this computer that all of a sudden cannot boot up at all. i turned on the power, and there's nothing on the monitor with the words "no signal" on the cpu itself, the busy light was off, HDD light is also off, in short, nothing is responing. however, all the fans are working, including air circulaton fan, VGA fan, proccessor fan. my first guess would be a dead motherboard as i can't boot up into either BIOS or windows

Test your power supply, just having the fans spin up does not rule out the PS........ Keep the old stuff running

power supply? but no lights was on at the front panel (both red/green lights)

Do like Linux OS2 says. It is almost certainly a power supply problem. When power is first applied to a PC a small amount of power is sent to the motherboard. This is just enough to power the north-bridge chip and fans, possibly at a slower speed. In this state the North-bridge chip sends a re-set signal to the CPU and holds it. This effectively stops the CPU from doing anything. Once the power supply has stabilised and all voltages are correct, full power is applied to the motherboard and a power good signal is sent to the motherboard which then removes the re-set signal to the CPU and allows the CPU to continue to boot the computer. This usually takes a few milliseconds. However, if there is a problem with the power supply, either a faulty regulator or some other problem, the power good signal never arrives and the CPU is held permanently in a reset state with just a minimal amount of power going to the motherboard. Saves a faulty power supply sending 12v to the CPU and memory and letting the smoke escape. Stuart

If you're comfortable working inside your machine, pull all the internal cards except the video (if present) out of the slots, then remove all peripheral equipment from the outside connectors except the monitor, mouse, and keyboard and try the boot again. Do you get anything now?

BEFORE you replace the mother board try this: Remove all your memory chips then turn the computer on. If you now hear the beeps on start-up, you have a bad memory chip which causes the problem you describe. Replace the memory chips one at a time until you find the bad one. If all fans are working, including the processor fan, the chances are your power supply is good. John 110

>> If all fans are working, including the processor fan, the chances are your power supply is good. << That is wrong. A faulty power supply can cause the fans to work but little else. In fact a faulty power supply can cause all sorts of strange things to happen and is the first thing to check when a computer starts behaving strangely. Check the power supply. It is the cheapest component in the computer and the easiest to replace. Stuart