No Items Appear in the Device Manager List When You Open It

When you open Device Manager, no devices appear in the list. Instead, a blank window appears.

This behavior occurs if the Plug and Play service is turned off (disabled).

To resolve this behavior, set the startup type for Plug and Play to Automatic. To do so, follow these steps:

1. Click Start, click Run, type services.msc, and then click OK.
2. Double-click Plug and Play.
   
   If you receive a Configuration Manager message, click OK.
3. In the Startup Type list, click Automatic, and then click OK.
4. Close Services.
5. Restart the computer.

This behavior is by design.

Plug and Play is a core operating system service, and therefore, it is best to not disable it. It runs in normal mode and in safe mode.