What components could cause POST to beep several times and fail during boot?

Answer 1

Improperly seated memory modules (RAM) can cause the computer beep rapidly during POST and to fail to boot. The other common problem is an improperly seated power connection (like the processor or fan power connectors) on the motherboard.

Answer 2

Yes, RAM can cause a beep code to occur as can a missing hard drive. (In the past, it would also cause a 1701 Hard Drive Failure message to appear on the screen if it was the primary hard drive or the same message with 1702 as the error code for the secondary drive in the machine.) The other common cause of beep codes is the machine fails to detect an available video output by way of a card or integrated video port. As David Bobb suggested, a failed chassis or CPU fan can cause a beep code as well, typically just a couple of quick beeps with a message on the screen indicating a fan failure. The more noticeable issue, though, in the case of the CPU fan is that the machine will shut itself off when the CPU gets too hot. This is accomplished by a thermistor built into the CPU as a form of self-defense against burning out due to improper cooling. If this happens, one must check to see if the CPU fan is clogged with dust or if the motor within it has burned out and thus a new fan needs to be installed.

Of course, to hear the beep codes, one must have a PC speaker installed in the machine since it will not be generated through the speakers attached to the sound card or integrated sound ports. The PC speaker is a small speaker that is connected to the motherboard inside the chassis and in some models of motherboards may already be soldered onto the board itself. For one who is familiar with the various beep codes, it can definitely be a quick and easy way to diagnose what is going on with a machine (or to point out a simple oversight when in the process of building said machine).

Problems with the CPU itself will generally not cause a beep code because the machine has no working CPU to start the POST process and, thus, the machine will not acknowledge that the power switch has been depressed. The same is true for a failing/failed power supply or motherboard. If you have this problem, the best thing to do is try to swap out the power supply first since that is about a $30 part for one of decent quality. If that doesn't fix the problem, then chances are that it will be either the CPU or motherboard. At that point, depending on the age of the machine, it might be best to consider replacing both (and possibly the RAM if the new board doesn't use the same type of RAM as the old one) and getting yourself an upgrade since replacement of either part could be expensive, especially if one buys directly from the manufacturer (such as Lenovo, HP, Dell, etc.).