Start a command prompt and set the following variable:

set devmgr_show_nonpresent_devices=1

Start Device manager from the command line:

devmgmt.msc

On the view menu, click Show hidden devices.

More info here:

http://support.microsoft.com/kb/315539

http://cs.thefoleyhouse.co.uk/blogs/karl/archive/2010/03/05/get-device-manager-to-show-nonpresent-devices-as-hidden-devices.aspx