Hey I just finished building my new computer, and I keep hitting the same probem. The computer will not start, as soon as I plug the power cord into the computer, the CPU fan spinsfor a second and then stops. The lights on the motherboard remain on as well, but no lights apear on the outter case. The motherboard has a built in On switch. I have tried turning on the computer both through the case and on the motherboard, but nothing happens I have now replaced just about every part. I have connected right now the following.
as soon as I plug the power cord into the computer, the CPU fan spinsfor a second and then stops.
That's normal, or at least not unusual.
The lights on the motherboard remain on as well, but no lights apear on the outter case.
Also normal. Each PSU has a small, independent 5 volt power supply called the Standby Power Supply. It's usually a 5 volt 2 amp (or so) power supply that is always on if the PSU is plugged in and the switch on the back of the PSU is "ON".
What kind of PSU do you have?
Double check all the cables. The 4 pin connector in the upper left corner of your motherboard powers the CPU. It must be plugged in.
Clear the CMOS RAM. Your motherboard manual will tell you how. Make sure the HSF is properly installed. Turn on your PC. If it's still broke, continue on.
Disconnect and unplug everything but the PSU, CPU & HSF, power & reset switches, and the system speaker from the motherboard. When you turn on the PC, you should hear a series of long single beeps. This will indicate a memory failure. (You do not have any memory installed, remember?)
If you get silence, either the PSU, motherboard, or CPU is bad. One other possibility is that you have something installed improperly in the case and it's shorting out the PSU. The only practical way to determine which is bad is to test by substitution. Most likely failure (in order) is PSU, motherboard, and CPU.
If you hear the beeps, turn off the PC and install one memory module. Turn on the PC and you should hear one long and two or three short beeps indicating a problem with the video card. Silence indicates that the memory module is shorting out the PSU. Long single beeps indicate a really bad memory module. Test and install the rest of the memory.
Turn off the computer. Install the video card and plug in the monitor. Turn on. System should boot and pass POST (single short beep), and you should see messages on the screen. If not, your video card or monitor is bad.
If you see messages, turn off PC and plug in keyboard and mouse.
If this works, start plugging the other components one by one.
This can be done before installing any the parts into the case. This is called "breadboarding" (from the 20's). I am a firm proponent of breadboarding. It lets me test all the parts before I install them in a case.