Show non-present devices in Device Manager
Time and again I forget the environment variable that makes the Windows device manager show devices that are not connected to the system, but installed anyway. I note it here now to have point for myself to find it more easily in the future :)
The easiest way to use it (if you don't want to configure it permanently through the "System" applet in the control panel) is to first start a command line (
cmd.exe) and then type the following commands:
set DEVMGR_SHOW_NONPRESENT_DEVICES=1 devmgmt.msc
In the device manager that starts up, you still need to enable the "Show Hidden devices" option in the "View" menu ("Ansicht/Ausgeblendete Geräte anzeigen" in a German Windows).
This will make the device manager show all devices that you installed but do not use anymore, e. g. USB drives you just connected once, mice and keyboards that have long been replaced etc. Sometimes those entries cause problems when you plug a similar device in, so deleting them might solve problems in that area.