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:
- Make sure that the main power connector is connected to the motherboard. Energizing a power supply without a load can instantly destroy it.
- Check all the fans to make sure they are properly connected. Starting up your computer with the CPU fan disconnected will result in your processor being irreparably damaged with minutes or seconds. The same goes for the chipset fan, if present.
- Make sure that all wires and cables are safely tied away from the fans and from sharp edges of the case. Neatness counts. Use plastic cable ties, not metal twist-ties. If you can't get plastic cable ties, then use electrical tape.
- Check that all of the power and data cables are properly and securely connected.
- Make sure that there are no tools, screws, or jumpers floating around in the case.
- Check that all expansion cards and RAM modules are securely seated.
- Make sure that the voltage setting on the power supply is the correct one for your region.
Setting the Correct Voltage on the Power Supply
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
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.
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.
- Start with the default settings. You can tweak them later if you like.
- Do make sure that the time and date settings are correct. You can use local time or Coordinated Universal Time (Greenwich time). Most Windows machines use local time, and most Unix and Linux machines use Greenwich time; but either system will work either way. You just correct the offset in the operating system clock if needed.
- If you don't know what a setting means, for the love of all things good and holy, leave it alone. Don't change any settings unless you know what you are doing.
- Make sure that all of your drives are showing up. If not, look to see if the drive controller is disabled in BIOS.
- If the drive controllers are enabled but the computer doesn't see any of the drives, shut down the machine, unplug it, and re-check all your drive connections.
- If you are using both an M.2 and a SATA drive, and only one of them shows in BIOS, it's almost certain that the M.2 drive is sharing the SATA header you used. Shutting down the computer and moving the SATA drive to another header should solve that problem. Consult the motherboard manual to see if a channel is shared and which SATA header it uses.
- Before installing your operating system, make sure that the optical drive or USB drive, depending on how you're going to install your operating system, is set as a bootable device. That's usually found in a section of the CMOS called "Boot Settings", "Boot Sequence", or "Boot Order." Some things just make sense.
- If you want to install the operating system to an M.2 drive, and you also have one or more SATA drives, disconnect the SATA drives before installing the operating system. That will force the OS to install to the M.2 drive, which is where you probably want it.
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 .
Try Backblaze Unlimited Online Backup for free!
Backup and sync your files anywhere with GoodSync
Newest Page: How to Build a Video Editing Computer
Buy a barebones computer kit at Amazon
As an Amazon Associate I earn from qualifying purchases. All product links on this page are monetized.