How to Build a PC, Step by Step

Building a PC is mostly plugging things into the only place they fit. It takes a first-timer two to four hours, and nearly all of that is cable work. Before you open a box, check that the parts work together: the build planner and the PC builder both check socket, memory type, size and power for you.

• A Phillips No. 2 screwdriver, ideally magnetic. It fits almost every screw in a PC.
• A large, clear table with a hard surface, not carpet.
• Good light, or a torch for the back of the case.
• Cable ties or velcro straps (many cases include some).
• A USB stick of 8 GB or more for installing the operating system.
• The motherboard manual. Keep it open throughout: it is the only guide that is exactly right for your board.

Fit the processor, the SSD, the memory and usually the cooler with the motherboard out of the case, sitting on its box. It is far easier than reaching into a case.

1. 1Lift the socket's retention arm and open the load plate.
2. 2Line up the processor using the small triangle on one corner, which matches a triangle on the socket. Intel processors also have notches on two edges that fit tabs in the socket.
3. 3Lower it straight down into place. Do not slide it or press it in; it should drop in under its own weight.
4. 4Close the load plate and push the arm down under its clip. It takes real force, and that is normal. On Intel and AM5 boards the plastic cover pops off as you close it; keep it in case you ever need to return the board.

1. 1Find the M.2 slot the manual recommends for your boot drive, usually the one nearest the processor. It is the fastest.
2. 2Remove its heatsink cover if it has one, and peel the plastic film off the thermal pad underneath.
3. 3Slide the drive into the slot at a slight angle, about 30 degrees, then press it flat.
4. 4Secure it with the screw or tool-free latch, then put the heatsink back.

With two sticks, use the two slots the manual names, which on most four-slot boards are the second and fourth from the processor (often labelled A2 and B2). That runs them in dual channel, which is noticeably faster than putting them side by side.

1. 1Open the clips at the end of each slot. Some boards only have a clip at one end.
2. 2Line up the notch in the stick with the key in the slot. It is off-centre, so the stick only goes in one way round.
3. 3Press down firmly with both thumbs at the ends until the clips click shut. It needs more force than you expect.

Every cooler mounts differently, so follow its own instructions. Most tower coolers can go on now; an all-in-one liquid cooler is usually easier once the board is in the case, because the radiator mounts to the case.

• Peel off the protective film on the cooler's base. Forgetting it is the most common reason a new build runs hot.
• If the cooler has thermal paste already applied, use that and add nothing. Otherwise put a pea-sized dot in the middle of the processor; the cooler's pressure spreads it.
• Tighten mounting screws a little at a time, alternating corners, so the pressure stays even.
• Plug the cooler's fan into the header labelled CPU_FAN. An all-in-one's pump goes on the header labelled AIO_PUMP or PUMP if the board has one.

1. 1Take off both side panels and set the glass one somewhere it cannot fall.
2. 2Check the standoffs, the small brass or black posts the board screws onto. Most cases come with them fitted for ATX. Each one must line up with a hole in your motherboard; a standoff with no hole above it can short the board, so remove any extras.
3. 3If your board did not come with its rear I/O shield already attached, clip the shield into the back of the case now, from the inside. It is easy to forget and needs the board out to fix.
4. 4Fit the power supply if the case design puts it in first (most do, in a bottom shroud). Fan facing down if the case has a filtered vent underneath, otherwise facing up.

1. 1Lower the board in at an angle, rear ports first, so they line up with the I/O shield.
2. 2Settle it onto the standoffs and check the screw holes line up.
3. 3Screw it down, snug but not tight. Start with the middle screw, which most cases make a locating pin.

Route each cable through the case's cut-outs from behind the motherboard tray before plugging it in. It is far easier than threading them afterwards.

• The 24-pin ATX cable goes to the wide connector on the right edge of the board.
• The 8-pin EPS cable (labelled CPU on the power supply side) goes to the top-left corner of the board. Some boards have a second 4 or 8-pin socket beside it; the manual says whether your processor needs it. Plug it in if you have the cable.
• Front panel USB and audio cables go to their headers along the bottom edge. The USB-C header is small and fragile, so push it in straight.
• SATA drives each need a SATA data cable to the board and a SATA power cable from the power supply.

The case's power button, reset button and lights connect with small single-pin plugs to a header in the bottom-right corner of the board. The exact layout is printed in the manual and usually on the board itself.

• Power switch (PWR_SW or POWER SW): which way round does not matter.
• Reset switch (RESET SW): which way round does not matter.
• Power LED (PLED + and PLED -): polarity matters. The positive wire is usually the coloured one.
• Drive activity LED (HDD_LED): polarity matters.

1. 1Remove the expansion slot covers on the back of the case that line up with the top long PCIe slot, usually two or three of them.
2. 2Open the clip at the end of the top PCIe x16 slot. It is the one wired at full speed.
3. 3Line the card up and press it straight down until the clip clicks.
4. 4Screw its bracket to the case, then fit any support bracket that came with a heavy card.
5. 5Connect its power: one, two or three 8-pin PCIe cables, or a single 12V-2x6 (12VHPWR) cable on many newer cards.

• Front and bottom fans pull air in; rear and top fans push it out. The arrows on a fan's frame show which way the air moves.
• Plug case fans into the SYS_FAN or CHA_FAN headers, or into the fan hub the case came with.
• An all-in-one radiator works best mounted at the top, or at the front with the tubes at the bottom, so the pump is never the highest point of the loop.

Plug the monitor into the graphics card, not the motherboard. The motherboard's own video ports only work with a processor that has graphics built in, and even then they are not the card's.

1. 1Switch the power supply on at the back (the side marked I) and press the case's power button.
2. 2Wait. A first boot with new memory, especially DDR5, can show a black screen for one to several minutes while the board trains the memory. This is normal; do not switch it off.
3. 3Press Delete (or F2) at the logo to enter the BIOS.
4. 4Check the BIOS sees your processor, all your memory and your SSD.
5. 5Turn on XMP (Intel) or EXPO (AMD) in the memory settings. Without it, memory runs at a slower default speed, not the speed on the box.

1. 1On another computer, make a Windows installer with Microsoft's Media Creation Tool and a USB stick of 8 GB or more.
2. 2Plug it into the new PC, start it, and pick the USB stick from the boot menu (often F8, F11 or F12).
3. 3Install to your SSD. You can skip the product key and add it later.
4. 4Once at the desktop, install the chipset driver from AMD or Intel, or from your motherboard maker's support page, and the graphics driver from NVIDIA, AMD or Intel.
5. 5Run Windows Update until nothing new appears.

Most boards have four small debug lights near the memory slots, labelled CPU, DRAM, VGA and BOOT. The one that stays lit tells you where it stopped.

• Nothing at all: check the power supply switch, the wall socket and the 24-pin cable, then the power switch plug on the front panel header.
• CPU light: reseat the 8-pin CPU power cable, then check the board's BIOS supports your processor (see the BIOS update tip above).
• DRAM light: reseat the memory, pressing until both clips click. Then try one stick alone in the slot the manual names for a single stick. Remember the first boot can take minutes.
• VGA light: check the graphics card is fully in its slot, every power cable is seated, and the monitor is plugged into the card.
• BOOT light: the PC works but finds nothing to start. Check the SSD is seated and the USB installer is selected in the boot menu.

Once it is running, check the processor's temperature at idle and under load with your motherboard's software or a free tool like HWiNFO. A processor that is very hot at idle usually means the cooler's protective film is still on or the cooler is not seated evenly.