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When one remove hardware or a service, then sometimes Windows thinks that the hardware or service still exists and they roam about as ghost devices in the Device Manager. Ghost devices can cause slow boot and other erratic behavior because Windows tries to communicate with a device which isn't there.

To make sure that no ghost devices exists, add the following STRING values to the registry (They will become environment variables):

[HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Control \Session Manager \Environment]
DEVMGR_SHOW_DETAILS = "1"
DEVMGR_SHOW_NONPRESENT_DEVICES = "1"

Then start the Device Manager and select "View" in the menu and select "Show Hidden Devices". Now it should show all devices registered in your system, making it possible to remove any ghosts which shouldn't be there. Devices that are greyed out are inactive(not started), if the same device is listed multiple time then consider removing the inactive ones.

More Info MS KB Q241257
More Info MS KB Q304514
More Info MS KB Q310126
More Info MS KB Q315539

Credits regedit.com