Find the culprit

Open Task Manager (Ctrl+Shift+Esc) → CPU column (click to sort descending). The top process is consuming the most CPU.

Common offenders

  • WmiPrvSE.exe (WMI Provider Host) — usually caused by another process querying WMI in a loop. Run the WMI diagnosis in Event Viewer.
  • antimalware service executable (MsMpEng) — Windows Defender doing a scheduled scan. Let it finish; if persistent, add your main drive to the exclusions list.
  • svchost.exe — right-click in Task Manager → Go to Services to see which service under svchost is spiking. Windows Update is a common cause right after booting.

Disable Search Indexing temporarily

Services.msc → Windows Search → Stop. If CPU drops dramatically, the index is rebuilding. It will settle after 30–60 minutes and can be re-enabled.

Check for malware

Persistent 100% CPU with no obvious cause — run Malwarebytes. Cryptominers run under disguised process names.