To help you keep your device secure, Windows Security monitors your device for security issues and provides a health report, which appears on the Device performance & health page. The Health report alerts you to common issues in four key areas and offers recommendations to remedy them.
For more info on Windows Security see Stay protected with Windows Security.
View the Health report for your device in Windows Security
In the search box on the taskbar, type Windows Security, and then select it from the results.
Select Device performance & health to view the Health report.
Note: If your device is part of an organization, your administrator may not have granted you permission to view Device performance & health.
The Health report starts off by showing you the last time a Device Health scan was run. The time displayed should be basically the current time, as Windows Security tries to run a Device Health scan when you open the Device performance & health page.
Beyond the time of last scan you'll see the status of the key areas that Device Health monitors:
Storage capacity - Is your system running low on disk space?
Apps and software - Is any of your software failing, or in need of an update?
Battery life - Is anything putting an extra strain on your PC's battery? You might not see this on on a desktop PC that is always plugged in.
Windows Time service - Having your system set to the correct time is important for a lot of system processes. Windows Time service automatically synchronizes your system clock to an internet-based time service so your system time is always correct. If this service is off, or failing, Device performance & health will let you know so you can fix it.
What if the Health report says there are problems?
A green check means everything is fine, but if you see a yellow mark that means something needs attention. Click the item to see what recommendations Device Health has for you.
For help resolving performance issues on your Windows 10 PC, see Tips to improve PC performance in Windows 10.
For help freeing up space on your device, see Free up drive space in Windows 10.
Make sure you have the latest updates installed by checking Windows Update. See Windows Update: FAQ.
If all else fails it may be helpful to use Fresh Start to do a clean installation of Windows. Fresh Start can usually preserve your data, but it's always a good idea to have tested backups of your data. For more information on Fresh Start see Give your PC a Fresh Start.