Checking the PC uptime in Windows can be done using the Task Manager. Open Task Manager by pressing Ctrl + Shift + Esc, then navigate to the Performance tab and select CPU. In there, find the value of Up time which tells you the duration your system has been running after the last full system startup. You may also opt to use Command Prompt or PowerShell should you want to use command-based checks. The purpose of checking PC uptime could be troubleshooting or checking if there was a recent restart, among others.