When you once connected for example a memory stick, this device will never be uninstalled again on your machine. Normally you cant see it anymore, until you reconnect the device. but you can force the device manager to show the hidden devices:
set the environment variable (properties of my computer):
start device manager
start a new Command Prompt (cmd.exe)
enter “set devmgr_show_nonpresent_devices=1″
enter “start devmgmt.msc” to start the device manager
Click on View/Show hidden device, now you see the hidden devices as grey icons..