So, yesterday I spent a few hours building my first computer ever. I tried to be careful, to do everything properly and not mess anything up, and I thought I did a pretty good job. I spent about an hour troubleshooting a problem that turned out to be I had a PCI-E power cable plugged in to my CPU's power slot, and finally my system was POSTing and booting properly. I hooked it up to my monitor, mouse and keyboard, and was finally excited to have it all set up.
At this point, I set the boot-drive to the DVD drive and put in my Windows 7 installation. It booted up fine and I started to install Windows 7 on my SSD. After awhile (I think Windows had gotten to the "Completing installation" step of the install) the computer restarted for like a 3rd or 4th time, but this time it started to randomly hang on the motherboard BIOS screen (gave like "F8 for BIOS" and a few other options). I tried to press something to enter in to the BIOS, but it seemed to be frozen and nothing was responding. At this point I (perhaps too hastily) turned off the computer to try to restart, but when I did there was no signal being delivered to the monitor. I opened up the computer after a little bit and found that two of the built-in LEDs that are supposed to indicate POST problems were lit: the ones for the RAM and the CPU. At this point, I'm completely lost as to what to do. I'm not completely computer-illiterate or anything, but I honestly have no clue what I did wrong or what caused this unexpected problem after the computer finally seemed to be booting properly. I've tried removing the sticks of RAM, the video card, and all the hard drives; but nothing has caused the system to even POST. It's just the same thing whenever I turn the computer on: all the fans spin up, components appear to be working, but the CPU and RAM POST lights come on.
Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.
Make sure you plug the CPU power cable in. The system will not boot without it.
I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.
You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.
If no beeps: Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.
At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.
The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.
A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.
This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.
If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.
Silence or long single beeps indicate a problem with the memory.
Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST. At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.
Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.