Type "Gadgets" in the search bar in the Start Menu (Windows's orb), and click on "View list of running gadgets", so you'll be able to see the real name of the Ghost Gadget. Then, you could try to find it and uninstall it.
There's also "Restore gadgets installed with Windows" option; you could use it too -- it'll, as you may have already figured out, delete all the gadgets you could have possibly downloaded and keep only those that came with Windows.
I hope that helps.
PS: You are sure it's a Windows Gadget, aren't you?