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Firing Up Your Homebuilt Computer for the First Time


The moment of truth has arrived!

If you skipped the previous page, please take a moment to run through this checklist prior to plugging your computer into a power source:


Setting the Correct Voltage on the Power Supply

The voltage selector on the back of the power supply is set to 115 volts

Most computer power supplies have two input voltage settings, usually taking the form of a small slider switch. Make sure that this switch is set to the correct voltage for your part of the world before you plug the computer into a power source.

Computers and other delicate electronic devices should always be plugged into, at a minimum, a surge protector. An uninterruptible power supply is even better.

In the United States, the correct power setting will be 110 - 120 volts. In your part of the world... Well, I really have no idea. Ask someone local if you are unsure about it.

Once you're sure your power supply is set to the correct voltage for your region, plug the power cord into the power supply and the other end into your surge protector or uninterruptible power supply. Hook up the keyboard, monitor, and mouse to their appropriate connectors if you haven't already, and press the power button.

And pray.


The CMOS Setup Screen

CMOS Setup screen on a computer that is being booted up for the first time ever

If you have done everything correctly, after a few seconds you will hear a delightful beep as the computer passes its very first POST (Power-On-Self-Test), and you should be greeted by a screen that looks vaguely like the one in this picture. This is called the CMOS Setup Screen or BIOS Setup Screen.

If you see something that looks like the picture shown here, then pat yourself on the back. And exhale. Your homebuilt computer is alive!

If you don't see something that looks vaguely like the picture shown here, then visit this page for some troubleshooting ideas.

The CMOS Setup Screen (or BIOS Setup Screen) is where you set all the low-level settings that your computer needs to be capable of, well, being a computer. This is all your computer is capable of doing until you install an operating system on it, and the settings you select will affect the way your OS performs.

Once you install an operating system, you may have to press DELETE, F2, F10, or some other key to get to the Setup screen again if you need to. Consult the motherboard manual if you're unsure how to get back into setup.

Video card being inserted into computer case with eBay logo in top left corner

Because your computer has no operating system at this point, you may also get an error message that says, appropriately enough, something along the lines of "No operating system found," maybe with some aural alarms just for good measure. That's nothing to worry about because your computer, in fact, does not have an operating system yet. So consider it an observation, not an error.

Most computers come with CMOS settings designed for Windows and to be good settings for the majority of people using that operating system, so you may not need to do anything at all except set the hardware clock. The settings the computer comes with are called the "default" settings, and they're suitable for most users.

That's good for me, because there are too many BIOS versions out there for me to really guide you along at this point. You'll simply have to read the motherboard manual and follow the instruction given there. But here are a few basic suggestions for things you can check and do during first power-on.

Once you've finished CMOS setup, saved the settings, and rebooted, you're ready to reboot into the boot media and install the operating system.

I hope you've enjoyed building your own computer. Now that your computer's finished, don't for forget to protect your machine from viruses and hackers and decide on a backup strategy. In fact, I suggest you download and install antivirus software right now, before you do anything else.

If you would like to see your computer-building experience documented on this site, please send an email to .

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