You can view which type of Windows Defender scan is in progress and see how long it has been running.
Open Windows Defender by clicking the Start button , clicking All Programs, and then clicking Windows Defender.
If a scan is in progress, the progress is displayed until the scan is complete. If the scan is complete, the status will display the scan results, and the date and time that the scan completed.
To view when your computer was last scanned for spyware and other potentially unwanted software, check the Status area on the Windows Defender Home page.