What you are doing when you build a PC

Building a PC means installing components into a case and connecting them so they work together. You are not soldering circuits or writing code — you are plugging parts into slots, screwing things down, and running cables. Most connections only fit one way, so you cannot accidentally plug something into the wrong place. The hardest part is usually not the building itself, but knowing which parts to buy so they work together.

This guide assumes you have already chosen your parts and have them in front of you. If you are still deciding what to buy, the category page "How to Build and Assemble Your Own PC" walks through that decision. This article covers only the physical assembly — the order of steps, where each part goes, and what to watch out for.

Key Takeaways

  • Install the power supply in the case first, then the motherboard, then everything else — this order keeps you from damaging parts with static electricity or accidentally bending pins.
  • The CPU, RAM, and M.2 drive install directly into the motherboard before the motherboard goes in the case, not after.
  • Most connections are keyed so they only fit one way; if something does not slide in easily, stop and check the alignment rather than forcing it.
  • You do not need thermal paste if your CPU cooler comes with it pre-applied; check the bottom of the cooler before you buy paste separately.
  • After assembly, you will need to install Windows or another operating system from a USB drive before the PC will start up normally.

Prepare your workspace and protect against static electricity

Work on a non-carpeted surface if you can — a kitchen table or wooden desk is better than carpet. If you must work on carpet, touch a metal part of the case every few minutes to discharge static electricity. You can also buy an anti-static wrist strap for about ten dollars; clip it to the case while you work.

Lay out all your parts before you start so you know you have everything. Check your motherboard manual — it came in the box or you can read it from the manufacturer's website using the model number. The manual shows you exactly where each connector goes, and you will need it during assembly. Keep it open next to you.

Install the power supply in the case

The power supply is a heavy metal box that goes in the bottom or back of the case, depending on your case design. Look inside your case for a rectangular opening with four screw holes around it. The power supply slides in with the fan facing down (if your case has ventilation holes in the bottom) or facing into the case (if it does not). Align the screw holes and fasten it with the four screws that came with the power supply.

Do not plug the power supply into the wall yet. The switch on the back should be in the OFF position. You will turn it on only after everything is installed and you are ready to test.

Install the CPU and RAM on the motherboard before it goes in the case

Lay the motherboard flat on a clean surface with the component side facing up. You will install the CPU and RAM now, while the motherboard is outside the case — this is much easier than reaching inside the case later.

Installing the CPU: Open the CPU socket by lifting the retention arm on the side. Line up the notches on the CPU with the keys in the socket — they only fit one way. Gently place the CPU in the socket without forcing it; it should sit flat without pressure. Lower the retention arm to lock it in place. Do not touch the gold pins on the bottom of the CPU or the contacts inside the socket.

Installing RAM: Open the clips on both ends of the RAM slot. Align the notch in the RAM stick with the key in the slot and press down firmly until both clips snap closed on their own. RAM requires more force than you might expect — if it does not click, you are not pressing hard enough. One click on each end means it is seated correctly.

Install the CPU cooler and thermal paste

Check the bottom of your CPU cooler. If it has a clear plastic film or sticker, peel it off — that is the protective covering, not part of the cooler. If the bottom is shiny metal with no paste visible, you need to explore thermal paste before installing the cooler.

If you need to explore paste, use a small amount — about the size of a grain of rice in the center of the CPU. Do not spread it; the cooler will spread it when you press down. If your cooler came with a tube of paste, use that. If not, any standard CPU thermal paste works.

Follow your cooler's manual for mounting. Most coolers have a bracket that screws to the motherboard, then the cooler itself clips or screws to the bracket. Tighten screws in an X pattern (opposite corners first) so the cooler sits flat. Do not over-tighten — snug is enough.

Install the M.2 drive and other storage on the motherboard

An M.2 drive is a small stick about the size of a stick of gum. Find the M.2 slot on your motherboard — the manual shows you where. Remove the small screw and standoff (a tiny metal post) if there is one. Insert the drive at a 30-degree angle into the slot, then press down and screw it in place. The drive should sit flat against the motherboard when tightened.

If you are using a 2.5-inch SSD or a 3.5-inch hard drive, you will install those in the case later, after the motherboard is mounted. For now, just set them aside.

Mount the motherboard in the case

Look inside your case for brass-colored posts sticking up from the bottom. These are standoffs — they keep the motherboard from touching the metal case and causing a short circuit. Your case probably has more standoff holes than you need. Line up the screw holes on your motherboard with the standoffs and install only the standoffs you need. Remove any extras so they do not touch the back of the motherboard.

Carefully lower the motherboard into the case and align the screw holes with the standoffs. Screw the motherboard down, tightening in a star pattern so it sits flat. Do not over-tighten — hand-tight is enough. The I/O ports (USB, audio, network) should line up with the rectangular opening at the back of the case.

Install the graphics card and other expansion cards

If you have a graphics card, find the PCIe slot on the motherboard — usually the longest slot, closest to the CPU. Open the retention clip at the end of the slot. Remove the metal bracket from the back of the case that covers the slot opening. Align the card with the slot and press down firmly until the retention clip snaps closed. The card should sit flush with the motherboard. Screw the bracket to the case so the card does not move.

If you have other expansion cards (sound card, network card, etc.), install them the same way in the remaining PCIe slots. Most modern PCs do not need these — the motherboard has audio and networking built in.

Install storage drives and connect power cables

If you have a 2.5-inch SSD or 3.5-inch hard drive, mount it in a drive bay using the four screws that came with the drive. Most cases have bays designed for these drives. Slide the drive in and screw it down on both sides.

Now connect the power cables from the power supply. The main 24-pin connector plugs into the motherboard — it is large and only fits one way. The 8-pin CPU power connector goes near the CPU socket. If your graphics card needs power, a 6-pin or 8-pin connector plugs into the card. SATA drives need a SATA power cable from the power supply and a SATA data cable from the motherboard. Check your motherboard manual for the exact locations of each connector.

Route cables behind the motherboard tray if your case has one, or along the sides of the case. This keeps cables out of the way of fans and makes the case easier to work in later.

Connect case front panel connectors and test before closing

Small connectors from the case front panel (power button, reset button, LED lights) plug into a header on the motherboard. The manual shows you exactly where. These are small and straightforward to get wrong, but they are not critical — if you get them backwards, the button just will not work, and you can fix it later. The power button is the most important one to get right.

Before you close the case, do a final check: all power connectors plugged in, RAM and CPU cooler seated, no loose screws inside the case, no cables touching fans. Turn on the power supply switch at the back. Press the power button on the case. The fans should spin and lights should come on. If nothing happens, turn off the power supply and check your connections. If the PC starts, let it run for a few seconds, then turn it off and close the case.

Frequently Asked Questions

Do I need to install Windows before I close the case?

No. You can close the case first. To install Windows, you will need a USB drive with Windows on it and a product key. Plug the USB drive into a USB port, turn on the PC, and follow the Windows installation steps. The PC will guide you through it.

What if the PC does not turn on after I close it?

The most common causes are a loose power connector, RAM not fully seated, or the power supply switch set to OFF. Open the case, check that the 24-pin motherboard connector and 8-pin CPU connector are fully plugged in, and make sure both RAM sticks click into place. Try again.

Can I install the CPU cooler after the motherboard is in the case?

It depends on your cooler and case. Some coolers are easier to install with the motherboard outside the case because you have more room to work. Check your cooler's manual. If it is a large tower cooler, install it before the motherboard goes in the case.

How much thermal paste should I use?

A small amount — about the size of a grain of rice or a pea — in the center of the CPU is enough. Too much paste can actually make cooling worse. If your cooler came with paste pre-applied, do not add more.

What if a cable does not reach where it needs to go?

Route it the long way around the case, behind the motherboard tray if there is one. If a power cable is too short, you may need a cable extension, which costs about ten dollars. SATA data cables are cheap and come in different lengths if you need a longer one.