The Central Processing Unit (CPU) is the brain of your computer. A computer with a bad CPU cannot properly run software or perform useful tasks.
With average technical skills, you can learn to tell if your PC has a bad CPU or if its problems stem from other causes.
In most cases, a non-functional CPU will leave your computer completely unresponsive; in limited circumstances, the CPU may misbehave only on certain occasions.
One major cause of CPU problem is overheating. Overheating can cause damage to your CPU. In some cases, the damage may not be permanent.
CPUs generally have their own cooling fans. If the fan is choked with dust or is otherwise running poorly, you may occasionally see blue screens and other erratic behavior from your PC. Prolonged overheating can destroy the CPU. So, if you suspect a bad fan, have it fixed as soon as possible.
Your computer contains a Basic Input-Output System (BIOS). One of the major functions of the BIOS is to checks your PC when you turn it on. If the BIOS detects hardware problems that will not permit the computer to start, the computer produces a series of beep sounds. The AMI BIOS beeps five or seven times if the CPU is bad.
Many times, people use computers with bad processors without them knowing. This does not mean that the subtle symptoms of bad CPU are not noticeable. They sometimes wrongly attribute these symptoms to other problems related to viral attack.
Sometimes, the computer may turn on, but no beep sound, no display. This means the computer does not do Power-On Self Test (POST).
In some cases the computer may power on, run the POST but turns off immediately.
In another cases, the screen may freeze during the Windows logo screen (when loading the Operating System). Or rather the computer will power on, but the screen freezes after using the computer for a few minutes.
System halt errors (famously known as blue screen of death) usually happens when the processor is faulty.
When your processor is confirmed to be bad, it is best you find a replacement for it. In this case, you will need the services of a qualified computer technician or hardware Engineer. DO NOT try to do it yourself if you are not technically trained to do so. Else, you may damage the computer motherboard, thus causing more havoc to your machine.