How to check your PC's health
A slow or noisy computer is not always a dying one. Five checks tell you where the problem is, and most of them take less than a minute.
1. The drive
The drive is the part that most often fails without warning, and it holds your files. Every modern drive keeps a health log called SMART.
On Windows, open PowerShell and type Get-PhysicalDisk: the HealthStatus column should say Healthy. On macOS, Disk Utility shows the SMART status of the internal drive. On Linux, smartctl -a /dev/sda (package smartmontools) prints the full log.
- Reallocated or pending sectors above zero on a hard drive: back up now.
- On an SSD, look at the wear indicator (Percentage Used): above 80 %, plan a replacement.
2. The battery
A laptop that dies after an hour usually has a worn battery, not a broken motherboard. On Windows, powercfg /batteryreport creates a report that compares the design capacity with the current full charge. On macOS, System Settings, Battery, Battery Health. On Linux, upower -i with the battery path.
- Below 80 % of the design capacity, the battery is worn but usable.
- Below 60 %, replacing it changes the daily use of the laptop.
3. Temperatures
Fans that roar for no reason often mean dust or dried thermal paste. A processor that stays above 90 °C under load slows itself down to protect itself, and the whole computer feels slow.
4. Startup and free space
Too many programs launched at startup, or a system drive more than 90 % full, slow down any computer, even a recent one. Remove what you do not use before buying anything.
5. Security
Check that an antivirus is active and up to date, and that the system still receives updates. Windows 10 stopped receiving free security updates in October 2025.
The tool
KDL Diag runs these checks in about two minutes, changes nothing on the computer and gives a score out of 100 with a PDF report anyone can read.