I was in the middle of doing my EVERYDAY stuff (facebook and whatnot) when My PC just turned off. When I powered it back on, Everything came on, fans spun, drives spun, HDD LED lit up, but there was no post, no beeps, and the POWER LED did not light up at all.  I removed the RAM to see if it would beep, but no it did not.
...and the make and MODEL of your PC is ....??

What is the Operating System ??

What EXACTLY where you doing when it turned off ('everyday stuff' isnt specific enough)

Any recent changes?  New Software installed recently ?  Anything DOWNLOADED recently ?The PC itself is a custom build, using a BIO-Star G31-M4 with Pentium 4 2 GB RAM 160 GB seagate HDD Logisys PSU (500w) and an Nvidia GPU. I am running WINDOWS XP, and I was using Facebook when it went down. recent download is Simracway about 2 days agoPower down and re-start it a few more times and see if you get a Post beep...Only new hardware installed is the PSU as of 2 months agoSee above...may be a faulty PSU.I have done that several times. but nothing appears on screen and I get no post at all.
PSU works Beautifuly. As I said, EVERYTHING comes on and spins, even the HDD lights up. but I get no beeps when I take out the RAM, and I get no postBorrow a known good PSU of the same or greater wattage and swap it in there.I dont have one. OLD one is 250WUpdate....

        I proceeded to swap back to the original PSU, which is the 250W stock PSU that came with the original case. I removed all but the HDD and I still had the same issue, along with the matter that I forgot to mention that the machine will not turn off unless I unplug it.  My wife let me borrow her PC's stock 350W PSU, and still the same issue.  I then switched the CPU to the older Celeron D 2.4 Ghz. Still the problem persists.All components are running, but no power LED light up, and no post, only now the HDD isn;t spinning this time.  I may have to shell out 60 Bucks I don;t have to replace the MOBO. I am open to any other alternatives as to what else I may try.