How to Build a PC: The Complete Guide

Building your own PC is one of the most rewarding things you can do as a tech enthusiast. You get exactly the performance you need, at a better price than pre-built systems, with the satisfaction of knowing every component inside your machine. This guide walks you through the entire process from planning to first boot.

Planning Components Tools Assembly BIOS & OS Troubleshooting

1. Planning Your Build

Before buying a single component, define your goals. What will you use this PC for? Gaming, video editing, 3D rendering, general productivity, or a combination? Your use case determines your budget allocation and component priorities.

Define Your Budget

Set a realistic total budget and allocate it across components. As a rough guide:

Entry-level gaming / productivity (£400–£700): Ryzen 5 or Core i5, 16 GB RAM, mid-range GPU, 500 GB–1 TB NVMe SSD.
Mid-range gaming (£700–£1,200): Ryzen 7 or Core i7, 32 GB RAM, upper mid-range GPU, 1 TB NVMe SSD.
High-end gaming / content creation (£1,200–£2,500+): Ryzen 9 / Core i9 or Threadripper, 32–64 GB RAM, flagship GPU, fast NVMe storage.

Compatibility Checklist

Compatibility is the most common source of mistakes. Before purchasing, verify:

CPU socket vs. motherboard socket — e.g. AM5 CPUs require AM5 motherboards; LGA1851 CPUs require LGA1851 boards.
RAM type and speed — DDR5 motherboards require DDR5 RAM; DDR4 boards require DDR4. Check the motherboard's QVL (Qualified Vendor List).
Motherboard form factor vs. case — ATX, Micro-ATX, and Mini-ITX boards require matching or larger cases.
PSU wattage — Use a power calculator (e.g. OuterVision) and add 20–30% headroom.
GPU length vs. case clearance — Check your case's maximum GPU length specification.
CPU cooler height vs. case clearance — Check your case's maximum CPU cooler height.
M.2 slot availability — Confirm your motherboard has enough M.2 slots for your storage plan.

2. Understanding the Components

CPU (Central Processing Unit)

The CPU is the brain of your system. It handles all general computation tasks. Key specs to consider:

Core count: More cores benefit multi-threaded workloads like video editing and streaming. Gaming typically benefits more from clock speed than core count.
Clock speed (GHz): Higher base and boost clocks mean faster single-threaded performance.
TDP (Thermal Design Power): Determines how much cooling you need.
Integrated graphics: Some CPUs include an iGPU — useful if you don't have a dedicated GPU yet.

Motherboard

The motherboard connects all components. Key considerations:

Chipset: Determines overclocking support, PCIe lanes, and feature set (e.g. AMD B650, X670E; Intel B760, Z890).
Form factor: ATX (full-size), Micro-ATX (compact), Mini-ITX (small form factor).
VRM quality: Critical for overclocking and high-TDP CPUs.
Connectivity: Number of M.2 slots, USB ports, PCIe slots, and rear I/O.

RAM (Memory)

RAM stores data your CPU is actively using. Key specs:

Capacity: 16 GB is the minimum for gaming in 2025; 32 GB is recommended for content creation.
Speed: DDR5-6000 is a sweet spot for AMD Ryzen; DDR5-5600 for Intel. Faster RAM yields diminishing returns.
Dual-channel: Always install RAM in matched pairs (e.g. 2×16 GB) for dual-channel performance.
Timings (CAS Latency): Lower CL numbers mean lower latency — important for gaming.

GPU (Graphics Card)

The GPU renders images and is the most important component for gaming and visual workloads.

VRAM: 8 GB is the minimum for 1080p gaming; 12–16 GB for 1440p and 4K.
Resolution target: Match GPU performance to your monitor's resolution and refresh rate.
Power connectors: Ensure your PSU has the required connectors (e.g. 16-pin for high-end NVIDIA cards).
Length: Verify the card fits in your chosen case.

Storage

NVMe SSD (M.2): The fastest storage option. PCIe 4.0 NVMe drives offer 5,000–7,000 MB/s sequential read speeds. PCIe 5.0 drives push beyond 10,000 MB/s. Ideal for your OS and primary applications.
SATA SSD: Slower than NVMe (~550 MB/s) but cost-effective for secondary storage.
HDD: High capacity at low cost — suitable for bulk media storage, not for OS or applications.

PSU (Power Supply Unit)

The PSU converts mains power to the voltages your components need. Never skimp here — a poor PSU can damage your entire system.

Wattage: Calculate your system's total draw and add 20–30% headroom.
Efficiency rating: 80 PLUS Bronze, Silver, Gold, Platinum, or Titanium. Gold is the sweet spot for most builds.
Modular vs. non-modular: Fully modular PSUs allow you to only connect the cables you need, improving airflow and cable management.
Reputable brands: Seasonic, Corsair, be quiet!, EVGA, and Fractal Design are well-regarded.

CPU Cooler

Stock cooler: Included with some CPUs (e.g. AMD Wraith coolers). Adequate for stock speeds on lower-TDP chips.
Air cooler: Tower coolers (e.g. Noctua NH-D15, be quiet! Dark Rock Pro) offer excellent performance and reliability.
AIO liquid cooler: All-in-one closed-loop coolers (240 mm, 280 mm, 360 mm) offer superior thermal performance and aesthetics.

Case

Choose a case that supports your motherboard form factor and has adequate airflow.
Check GPU length clearance, CPU cooler height clearance, and radiator mounting positions.
Consider front panel I/O (USB-C, USB-A) and dust filter coverage.

3. Tools You'll Need

Phillips head screwdriver (magnetic tip): A #2 screwdriver handles the vast majority of screws in a PC build.
Anti-static wrist strap: Prevents electrostatic discharge (ESD) from damaging sensitive components.
Thermal paste: Required if your cooler doesn't include a pre-applied pad. Arctic MX-6 or Noctua NT-H1 are excellent choices.
Cable ties / Velcro straps: For cable management.
Good lighting: A well-lit workspace prevents mistakes.
A clean, flat surface: Work on a non-carpeted surface to minimise static risk.

4. Assembly — Step by Step

Step 1: Prepare Your Workspace

Clear a large, flat, well-lit surface. Ground yourself by touching a metal object or wearing an anti-static wrist strap. Keep all components in their anti-static bags until needed.

Step 2: Install the CPU

Open the CPU socket lever/latch on the motherboard.
Align the CPU with the socket — look for the triangle marker on the CPU corner matching the socket corner.
Gently lower the CPU into the socket — do not apply pressure; it should drop in with zero force (ZIF socket).
Close and lock the socket lever/latch.

Step 3: Install RAM

Consult your motherboard manual for the correct dual-channel slots (typically A2 and B2 for a 2-stick configuration).
Open the retention clips on the RAM slots.
Align the RAM notch with the slot key and press firmly and evenly until the clips click into place.

Step 4: Install M.2 SSD(s)

Locate the M.2 slot(s) on your motherboard (consult the manual for slot priority).
Remove the M.2 heatsink if present.
Insert the M.2 drive at a 30° angle and press down gently.
Secure with the retaining screw or clip, then reattach the heatsink.

Step 5: Install the CPU Cooler

If using a third-party cooler, install the backplate through the motherboard (if required).
Apply a small pea-sized amount of thermal paste to the centre of the CPU IHS (if not pre-applied).
Mount the cooler according to the manufacturer's instructions, tightening screws in a cross pattern to ensure even pressure.
Connect the cooler fan(s) to the CPU_FAN header on the motherboard.

Step 6: Prepare the Case

Install the I/O shield (if separate) into the rear of the case.
Install motherboard standoffs in the correct positions for your form factor.
Install any case fans and route their cables.

Step 7: Install the Motherboard

Lower the motherboard into the case, aligning the rear I/O with the I/O shield and the screw holes with the standoffs.
Secure with the provided screws — do not overtighten.

Step 8: Install the PSU

Slide the PSU into its bay (typically bottom-rear of the case).
Orient the fan towards the vented bottom of the case (if applicable).
Secure with the four screws provided.

Step 9: Connect Power Cables

24-pin ATX connector — main motherboard power.
CPU power connector (4+4 pin or 8-pin EPS) — located near the top-left of the motherboard.
PCIe power connectors — for the GPU (6+2 pin or 16-pin).
SATA power — for any SATA SSDs or HDDs.

Step 10: Install the GPU

Remove the appropriate PCIe slot covers from the rear of the case.
Insert the GPU into the primary PCIe x16 slot (the top full-length slot) until it clicks.
Secure the GPU bracket to the case with screws.
Connect PCIe power cables from the PSU.

Step 11: Connect Front Panel Headers

Consult your motherboard manual for the exact pin layout. Connect:

Power switch (PWR_SW)
Reset switch (RESET_SW)
Power LED (PWR_LED)
HDD LED (HDD_LED)
Front panel USB headers (USB 2.0, USB 3.0, USB-C)
Front panel audio header (HD_AUDIO)

Step 12: Cable Management

Route cables through the case's cable management channels and behind the motherboard tray where possible. Use cable ties or Velcro straps to bundle cables neatly. Good cable management improves airflow and makes future upgrades easier.

Step 13: Final Check Before First Boot

All power connectors seated firmly.
RAM fully clicked into slots.
GPU seated and secured.
CPU cooler fan connected.
All case fans connected.
No loose screws or tools left inside the case.

5. BIOS Setup & Operating System Installation

First Boot & BIOS

Connect your monitor to the GPU (not the motherboard's display output, unless using integrated graphics).
Power on the system. Press the BIOS key (typically Delete or F2) as it boots.
In the BIOS, verify that your CPU, RAM, and storage are detected correctly.
Enable XMP / EXPO to run your RAM at its rated speed (it defaults to JEDEC speeds otherwise).
Set the boot order to prioritise your USB drive for OS installation.
Save and exit (F10).

Installing Windows 11

Create a bootable USB drive using the Microsoft Media Creation Tool on another PC.
Boot from the USB drive.
Follow the on-screen installer — select your language, edition, and the drive to install Windows on.
Choose Custom Install and select your NVMe SSD as the installation target.
Complete the setup, install drivers (chipset, GPU, audio, LAN) from the motherboard and GPU manufacturer websites.

Post-Install Driver & Update Checklist

Windows Update — install all available updates.
Chipset drivers — from AMD or Intel's website.
GPU drivers — from NVIDIA, AMD, or Intel's website.
Motherboard drivers — LAN, audio, USB, and any additional controllers.
Enable Resizable BAR (ReBAR) in BIOS if supported — improves GPU performance in games.

6. Troubleshooting Common Issues

Symptom	Likely Cause	Fix
No power at all	PSU switch off, unseated 24-pin connector, or faulty PSU	Check PSU rear switch, reseat 24-pin and CPU power connectors
Fans spin but no display	Monitor connected to motherboard instead of GPU, unseated GPU or RAM	Connect monitor to GPU, reseat GPU and RAM sticks
POST beeps / debug LEDs	RAM not detected, CPU not seated, or GPU issue	Consult motherboard manual for beep/LED codes; reseat components
RAM running at wrong speed	XMP/EXPO not enabled in BIOS	Enable XMP or EXPO in BIOS settings
System crashes / BSODs	Unstable RAM OC, insufficient PSU, overheating	Run MemTest86, check temps with HWiNFO64, verify PSU wattage
High CPU temperatures	Poor thermal paste application or cooler not seated correctly	Remount cooler, reapply thermal paste, check fan curve in BIOS
M.2 drive not detected	Drive not fully seated, or slot sharing bandwidth with another slot	Reseat drive, check motherboard manual for slot priority rules

Need Components for Your Build?

PC Gear UK stocks a wide range of CPUs, motherboards, RAM, GPUs, storage, PSUs, cases, and cooling solutions. Browse our categories to find everything you need for your build — with expert advice available if you need help choosing the right parts.