Custom built PC been working great for 3 years, then it stopped booting up. Well, that's not entirely true, but I'll explain further.

Basically you push the power button, fans come on whirling but the HD light never lights up, and nothing comes on the screen. I get no beeps from bios, and no indication that there is something wrong. Of course it used to be if I left it off for about 30 min after trying to boot it up, sometimes it would actually turn on and work fine.

However it's been 2 weeks since that last worked (should've just left it on grrr), and now it's pretty dead. I did the usual, pulled out the RAM, gfx card, bios battery - turned the PC on and no bios or beeps, just fans whirling.

Thought I must have either a dead motherboard or a dead CPU since it's not even getting to the bios. Bought a new bios battery, no dice. Bought a new motherboard and tried with all my old parts + new mobo... no dice. Went ahead and bought a new CPU, put it in last night, no dice.

Unless they shipped me a bad CPU, what could the problem be? Power supply?

Any help would be GREATLY appreciated!

For reference purposes here are my main components:

Maxtor DiamondMax 10 6V300F0 300GB Serial ATA7200RPM Hard Drive w/16MB Buffer
CoolerMaster TAC-T01-E1 Wave Master
Asus P5N32-SLI Deluxe
Antec TruePower 2.0 EPS12V 550W Power Supply
BFG GeForce 7900 GT PCI Express 256MB DDR3
Intel PentiumD 940 3.2GHz
Kingston HyperX KHX6000D2K2/2G 2GB Kit DDR2-750 PC2-6000

Sounds to me like your spending money before you should. If you removed all the components attached to you board and didnt get any beeps i would definately try plugging in into a new power supply first. or even if you or a friend have an old compatiable suppy around somewhere try that.

ohk lets take a step back you switch your machine on.do you get display?no display?

I do not get a display.

Really? Even though the fans are spinning and the light on the board is lit green?

yes that can happen! maybe just not enough power. that exact same thing happened to a computer i was fixing and when i tried another suppy, boom, up she came.

I too am having what would seem to be an identical problem so I will attempt to clarify.

During power up all the expected lights and fans turn on, however the monitor does not detect the computer and quickly goes in to power-save mode. My computer had been running for almost 2 years with and has had no substantial software or hardware changes in several months at least. I had turned the computer on for the day and when I returned several hours later it was off if its own accord. I too tried removing/replacing the RAM and the BIOS battery to no avail. Is it possible for a power supply to simply weaken over time and there by cause a computer brown-out?

check this first:
1-does your monitor give orage light
2-turn monitor brightness all the way up
3-if its not onboard GFX switch to onboard to check if its working
if all fails try this
What you can do is remove all hardware except for hard drive (with your OS on it),processor and one stick ram.do make sure all your cables is firmly connected especially your monitor signal and power cable.
turn pc on and check for new behaviour
??

If all is good then the setup that Sittas explained should take you to the bios screen at the minimum which would rule out the Mobo, CPU and RAM being bad.

Raj

If there are no beeps its not the video. You would get beeps, probably one long beep followed by two short (from my experience).
If there are no beeps but fan come on i would have to say remove everthing including hard drive and leave one stick of ram. then if this dont work try replace that one stick with another. then if nothing try power supply. i repeat, this has happened to me and it was the power suppy just not producing enough to fire up pc but enough for fans.