What to look for when buying a used PC

Second-hand PCs can be great value. They can also be someone else's problem, sold on before the fault becomes obvious. Knowing what to check - and what questions to ask - is the difference between a bargain and a repair bill.

Before you meet the seller

Do your homework on the listed specs first. Look up the CPU and GPU model, check what they're worth new and used, and compare that against the asking price. If a deal looks too good, there's usually a reason.

Ask the seller directly:

• Why are you selling it?
• How old is it and do you have the original receipts?
• Has it ever been repaired or had parts replaced?
• Does it have the original Windows licence, and is it tied to a Microsoft account?

You won't always get honest answers, but evasive or inconsistent replies are a signal worth taking seriously.

Check the physical condition

Inspect the outside of the case carefully. Heavy scratches, dents, or a case that's been forced open and bent suggest it's been used hard or worked on carelessly. Check all the USB ports, audio jacks, and card readers - wiggle them gently and make sure they're not loose or damaged.

Open the case if the seller allows it. Look for:

• Dust buildup - heavy dust means it hasn't been maintained, which raises questions about temperatures and longevity
• Bulging or leaking capacitors - small cylindrical components on the motherboard; the tops should be flat, not domed or crusty
• Burn marks or scorch discolouration anywhere on the board or around connectors
• Non-standard wiring or bodged repairs - mismatched cables, blobs of hot glue, or components that look like they've been swapped out in a hurry
• Bent CPU socket pins - if the cooler has been removed, take a careful look at the socket with a torch

Run these checks with the PC on

Don't hand over money without seeing the machine boot into Windows and running a few quick checks. If the seller won't let you, walk away.

Check the specs match the listing. Open Task Manager (Ctrl + Shift + Esc), click Performance, and verify the CPU, RAM capacity, and RAM speed. Cross-reference with what was advertised.

Run HWiNFO64 or Speccy to get a full picture of the hardware - GPU model, storage devices, motherboard. Download it on a USB drive beforehand if needed.

Check storage health. Download CrystalDiskInfo and run it. It reads the drive's internal health data (SMART). Any warnings, reallocated sectors, or a high power-on hours count on an HDD are red flags. SSDs show percentage of rated write endurance remaining.

Stress the GPU briefly. Open a demanding game or run FurMark for five minutes. Watch for artifacts, screen flickering, or a sudden crash. A card that's fine at desktop but fails under load has a fault the seller may or may not know about.

Check temperatures under load using MSI Afterburner or HWiNFO. A machine that immediately hits 95°C on the CPU under light load has a thermal paste or cooling problem.

Check for how many Windows activations remain and whether the licence is transferable. OEM licences tied to the original motherboard won't activate on a different machine if the board ever needs replacing.

GPU-specific checks

If the machine has a dedicated GPU, pay particular attention. GPUs are the most expensive component and the most likely to have been thrashed.

Ask whether the card has ever been used for mining. Mining workloads run GPUs at sustained high load for months at a time - often with aggressive power limits and inadequate cooling. A mined-on card may have degraded VRAM and shortened lifespan even if it appears to work fine in a short test.

Check the fans spin freely and quietly. Rattling or grinding fan bearings on a GPU are a sign of heavy use and mean a repair or replacement is coming.

Red flags that mean walk away

• Seller won't let you turn it on or run any checks
• Specs don't match what's shown in Windows
• CrystalDiskInfo shows drive warnings or errors
• Artifacts or crashes during a GPU stress test
• Burn marks, bulging capacitors, or signs of liquid damage inside the case
• No Windows licence or the activation is already flagged as invalid
• Price is significantly below market value with no clear explanation

When to get a pre-purchase check

If you've found a machine that looks good but you're not confident running the checks yourself, or if you want a more thorough assessment than a quick visual and a stress test allows, a pre-purchase inspection is worth considering. We can test the machine properly on the bench - including PSU load testing and component-level checks that aren't possible in a five-minute living room inspection - and give you a written report before you commit to buying.