Note: Not all computers have beep codes, some of the newer computers have LED's that light up that indicate the error or have a sound file to indicate the error.
A POST failure can be caused by any of the following situations.
1. New hardware conflicting with old hardware
2. Bad or failing hardware device.
3. Other hardware issue. (electrical shorts or incompatibilities.)
Warning: Some of the below steps recommend removing physical parts within the computer. While in the computer it is highly recommend that you be aware of electrostatic discharge and its potential hazards. ALWAYS ground yourself and your equipment. Ensure your computer is unplugged!
Note: Make sure your computer is turning on, if you press the power button and nothing happens (no lights, no sound, no fans, etc.) then this issue is not a NO POST but is an power related issue.
If any new hardware has been recently added to the computer, remove that hardware to make sure it is not the cause of your issue. If after removing the new hardware your computer works it's likely the computer is either not compatible with the new hardware or a system setting needs to be changed to work with the new hardware device.
1. Remove everything from the back of the computer except the power cable. Turn on the computer and see if it beeps normally. If the computer has never beeped also connect a monitor to the computer to see if any change occurs.
2. Check the stand-offs (the metal or plastic insulators) that keep your motherboard off and away from the case or housing. Ensure they are not grounding or shorting the motherboard out. If they are metal, ensure that the cardboard insulators are present. Ensure the motherboard is not grounding out to the case also at any other point.
3. If you are receiving a sequence of beeps consult your motherboard manual or the motherboard manufacturer's website for a listing of different beep codes and their explanation. These beep codes are meant as a method of quickly identifying what computer component is failing or bad.
4. Check to make sure power cables are not grounding or shorting to the case or other components. Ensure all ends are connected properly, securely, and snugly.
5. Make sure all fans are running in the computer. If a fan has failed (especially the heat sink fan for the CPU) your computer could be overheating and/or detecting the fan failure causing the computer not to boot.
6. If you were unable to determine by the beep code what is failing or do not have a beep code disconnect the IDE cables from the CD-ROM, Hard Drive, and Floppy drive from the Motherboard. If this resolves your post failure, attempt to connect each device one at a time to determine which device and or cable is causing the issue.
7. If the above recommendations still have not resolved the irregular POST, start disconnecting your expansion riser cards, these are the cards that are not essential to system operation. Break your motherboard down to the bare basics. Disconnect your floppy drive, CD/DVD ROM, and hard drives Your motherboard basics should have just the following: video card, RAM, motherboard and PSU (power supply unit). If this resolves the issue or allows the computer to post connect one card or device at a time until you determine which card or device is causing the issue.
8. If you continue to receive the same problem with all the above hardware removed attempt to disconnect the CPU and RAM from the Motherboard. Once done insert the CPU and RAM back into the computer to see doing this resolves your issue.
9. Ensure your PSU is of the correct size and power requirements for your system. Many newer motherboards and graphics cards are power intensive. Some newer graphics cards require their own separate power supplies. An underpowered PSU, will also cause system failure. Most new systems will not run well with less than 450W PSUs.
10. If after doing all of the above recommendations you continue to have the same issues unfortunately it is likely that you have bad or incompatible components, in particular RAM. Ensure your RAM is compatible with the motherboard. Many newer motherboards are very specific about what RAM sticks they will accept. Don't mix and match RAM speeds, type, or size.
11. If you have determined your components are compatible, then you have faulty hardware. The next step would be to test each component separately. You will need to find a working motherboard to test RAM with a diagnostic program like Memtest 86+. A faulty motherboard will need to be simply replaced. A bad PSU can only be replaced. Don't attempt to repair a bad or failing PSU. This is quite dangerous. High voltages and hazardous chemicals are present in PSU capacitors and other components – even when main power is disconnected. You can only replace a bad PSU.
12. If you keep getting the same failures after replacing CPUs, motherboards, and PSUs, there is a small chance that one of the peripheral cards is not compatible and causing damage or the card is conflicting with an internal integrated component. If you have integrated video or sound, you need to turn these off before using external cards.