Device Manager tends to hide devices that may have been in your system at one time or another. This sometimes occurs after your have installed a new sound card, video card, or a new USB device.
There are ways to make Windows Device Manager show these hidden devices.
You can either enter that at a command prompt, or add it to your environmental variables ( Start Menu --> Control Panel --> System --> Advanced ). Click the Environment Variables button. Under System Variables [user variables also works] click 'New', enter "DEVMGR_SHOW_NONPRESENT_DEVICES" with the value of "1").
After doing the above, open Device Manager, click View in the ToolBar, then Show Hidden Devices.
You'll see a lot more devices to work with then before you did this tweak.
This helps when you want to uninstall a driver for a piece of hardware that is long gone.
This can also be done via a Registry entry.
Open RegEdit and browse to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment.
Make a new String Value with a name of "DEVMGR_SHOW_NONPRESENT_DEVICES". Give it a value of "1".