Buying a used computer often seems the only option when you have a limited budget. And if you know where to look and you know what you're buying, it is possible to get a powerful piece of hardware for a fraction of the original price.

Even so, it would be unwise to buy a used PC or laptop at a low price without thoroughly testing the hardware. A blind purchase is likely to result in the seller ripping you off. If you're considering buying a used Windows PC, we'll outline the various tests you should run and considerations you should take into account to make a well-informed purchase.

1. Test the RAM

Random-access memory, or RAM, is your computer's short-term memory. It stores the information of current processes and uses the information to make your computer run smoothly.

A RAM malfunction occurs when a process writes data to RAM, but RAM returns different data when retrieving the same information.

If you buy a computer with faulty RAM, you will likely encounter crashes, distorted graphics, sluggish performance, and an endless stream of errors. Hence, it is imperative to test RAM before buying a used PC.

While various third-party tools are available to test RAM, we recommend using the Windows Memory Diagnostic tool. Before the test run, save any unsaved progress as the tool asks to restart your computer.

Here is how you can test the RAM with this tool:

  1. Open the Run prompt by pressing the Win + R keyboard shortcut.
  2. Type "mdsched.exe" and hit Enter.
  3. Click on Restart now and check for problems (recommended).
    Running a Memory Diagnostic Test in Windows 10

After following the above instructions, Windows will restart once, and after booting, the Memory Diagnostic tool will begin working. After the test run is complete, Windows will restart once again.

Upon restarting a second time, either you'll see the test results right away or need to use the Windows Event Viewer to look for them. To do this, follow these steps:

  1. Right-click on the Windows Start button and go to the Event Viewer.
  2. Go to Windows Logs and navigate to System.
  3. Click on Find under Actions in the right-hand pane.
  4. Type "MemoryDiagnostic" and click on Find Next.
    Checking the Result of MemoryDiagnosticTest in WIndows 10 Event Viewer

The Event Viewer will search for the string in its data and show the test run result.

2. Check the Health of Your Hard Drives

Checking the Hard Drives Health in Crystal Disk Info Tool in Windows 10

A faulty hard drive can cause various issues, including the inability to read from or write to the drive, frequent computer crashes, file loading that takes forever, and other issues. Hence, you should also check the hard drive before buying a used computer.

SSDs and HDDs last long and seldom fail, but it is essential to ensure their health is good, their temperature is within an acceptable range, and they do not have bad sectors or bad blocks.

You can check the health of hard drives using any third-party software, but we recommend CrystalDiskInfo. It's a free tool that shows you pretty much all the information you need to know about any hard drive you have installed.

First, download the CrystalDiskInfo tool and install it on your computer. As soon as you launch the tool, you'll see the statistics of all the drives on your computer. If you have more than one hard drive, you can switch between them by clicking on the arrow button in the top-right corner of the tool interface.

From all the stats the tool shows you, the health status and temperature are of the utmost importance. The health status of your hard drive should be Good, and its temperature should be between 30 °C and 50 °C. The temperature shouldn't go higher than 70 °C in the worst-case scenario.

Download: CrystalDiskInfo for Windows (Free)

3. Test Battery Health

The charging capacity of laptop batteries continues to decline over time. If the battery in the laptop you're about to buy has suffered substantial abuse, you may not get as much charge time and may even need a replacement.

Therefore, run a battery health check beforehand to avoid bearing this extra cost after the purchase. Follow these steps to generate a battery report:

  1. Type "cmd" in the Windows 10 search bar.
  2. Right-click on the Command Prompt app and click Run as administrator.
  3. Type “powercfg/batteryreport”.
  4. Hit Enter.
    Command Prompt Showing the Folder Where the Battery Report is Saved

The above process will generate a battery report and save it to a specific folder, which in most cases would be C:\Windows\System32\battery-report.

Analyze the battery usage and life estimates by thoroughly inspecting the battery report. You should ensure that the estimated battery life the battery gives after full charge is adequate, and if you have to replace it with a new one, factor in that cost when purchasing a used laptop.

You can also check the battery health using different battery health tools for more in-depth analysis.

4. Stress Test the CPU and GPU

If you intend to use your computer for resource-hogging work or play graphics-intensive games, make sure the CPU and GPU are sufficiently robust to withstand the stress you're planning to put on them. Stress-testing both components is the best way to find out.

A stress test pushes the computer hardware (CPUs, GPUs) to their maximum performance and monitors how well they handle this extreme load. If the PC stays stable during the stress test, you made a good choice since it won't crash or malfunction under heavy loads.

If the CPU or GPU fails during a stress test, they don't have enough endurance to handle heavy loads, and you'll likely have serious performance issues.

Check out our article on how to stress test CPU and GPU safely if you have never done so before.

5. Keep the Temperature of CPU and GPU Under-Check

Monitoring CPU and GPU Temperature Using NZXT CAM software in WIndows 10

When your computer shuts down during a stress test, it's because it's overheating at a critical temperature rather than being overburdened. If this happens, you can then decide whether you need an extra case fan, cooling kit, or anything else to keep the component's temperature at safe levels.

If you don't get the CPU and GPU temperature data during the stress test run, we recommend using dedicated software to keep their temperature in check.

NZXT's CAM software is highly recommended as its intuitive interface makes it easy to adjust the clock and fan speed to check the component's temperature under your preferred load.

Download: NZXT's CAM for Windows (Free)

Don't Buy a Used PC Before Running These Tests

Whether you're going to buy a decade-old PC or get a hand-me-down from someone else, running these tests will help you determine your computer's hardware's condition. Then you can decide whether you need to swap any components to get your PC properly running.

If you plan to replace any of the components, it's better to sell the old one on eBay, Facebook Marketplace, IT Connected, etc., to get a reasonable price.