Initial Boot-Up

It is time for the moment of truth. To see if this thing works!!

Before doing it, connect all of the external peripherals to the system. This includes the mouse, the keyboard, and the monitor as well as the main power cords for the monitor and main PC. You don’t need to connect anything else yet. Besides, if you are following this procedure, you won't have too many added parts installed yet. You can go ahead and attach the speakers and things, if you have the hardware installed, but the sound card will not be doing anything at this point.

Also, you need to have a valid system boot disk. Your system disk should have been ahead of time, as noted previously in this tutorial.
>> For more information, read System Disk Creation.

Stick your system disk into the A: drive.
Turn your monitor on and let it heat up a few seconds before proceeding.
Keep in mind what to expect. You may need to act quickly. The power LED should turn on, then fans should start spinning, the hard drive should power up. You will see the video BIOS screen first, then you will see the BIOS screen and it will proceed to count the memory. You may hear one beep from the PC speaker. You may also get a "CMOS checksum error" or another error saying the CMOS or time isn't set. Know what key(s) to hit to enter setup. This will be shown on the bottom of the screen. You will want to do this quickly. If you hear any weird sounds such as grinding, scraping, or loud whining, be ready to turn the system off immediately. Keep in mind that if you miss the stated sequence to enter the BIOS before the boot sequence moves on, there is nothing wrong with just hitting the reset button and rebooting until you do catch what it is.
Press the power switch. If it powers up, observe the system closely. As soon as the BIOS screen appears, press the appropriate key(s) and enter BIOS setup. The correct key combination should be visible at the bottom of the screen. Sometimes it pops by too quickly for you to see which keys to press. No problem. Don't hesitate to just hit reset and try again, as stated above. A lot of times, the key will do the trick.
After you are sitting in the CMOS area, just let it sit there while you take out a flash light and inspect the system. Make sure all the fans are running. Make sure all the fans are operating smoothly and not generating any strange noises. Make sure the case power LED is on. Make sure the floppy drive light is not stuck on. If it is, the ribbon cable is likely not properly aligned with Pin 1. If any of the fans are not spinning, turn the PC back off and plug the fan in. You do not want to run the PC for long without fans running, especially the CPU fan.
Basic troubleshooting:

Sometimes things do not work exactly as planned at this point. Sometimes the system will not power on at all. Sometimes it will power on, but you get no video. Sometimes you will get beep codes. Sometimes you hear the fans, but the rest of the PC just sits there and does nothing.

If things didn't go according to plan, troubleshoot the system. Walk mentally through the boot process and check all hardware as it goes. Think like the computer thinks, if you know what I mean. Here is a list of some of the more common problems.

The power does not even turn on. This sometimes happens on ATX machines and it usually tracks down to the fact that the power switch is not properly connected to the motherboard or it is not connected at all. Find the power switch lead and make sure it is connected to the motherboard, as described in Step 11. It’s a possibility that simply reversing the lead will do the trick. If this is the not the case, then make sure the motherboard is not grounded somehow. Make sure that the board is not touching the case (this is what the spacers are for). Make sure that none of the screws that hold the board in place are touching anything metal or any of the electrical pathways on the motherboard. If you have any doubt on this, you can remove each screw one at a time and place a washer on them. You do not need to remove the motherboard to do this.
The PC boots, but it is giving beep codes. This is actually better than having to track everything down on your own, because at least the PC is giving you a hint as to what is wrong. Consult the article on Beep Codes to see what it might mean. You can also use the PC Mechanic Beep Codes E-book available on the PC Mechanic CD to track it down for other BIOS versions. Often, these beep codes will not tell you exactly what the problem is, but will point you at the trouble device. This information will then get you pointed in the correct direction.
The fans come on, but you get no video or beeps. Sometimes, this is because some key component may not be plugged in well or may not be operational. Check the memory modules and the processor to be sure they are firmly installed. You might want to make sure the processor is actually working. One way that I have used to see if a processor is working is to remove or unplug the CPU fan and place your fingers on the CPU to see if it heats up real fast. If it does, its OK and don’t let it run this way for long. If it remains at room temperature for awhile, then there is no juice going through the processor and it may need replacing. Sometimes, you may need to track down a problem component through a process of elimination. You may need to replace parts one by one and then use that gray matter in your head to narrow down the problem. Also be sure you have the CPU jumper settings done properly and are not trying to run the processor on settings too high or too low.
The keyboard doesn’t seem to work. This one doesn’t happen too often, but if it does, your two trouble sources will be the keyboard itself or the keyboard controller on the motherboard. Hope it isn’t the second one.