For no reason that I can think up, I suddenly have a local disk Q: in Explorer. There is no hardware associated with it, it doesn't show up in Disk Manager, it's not a network drive, and everything I try to do with it results in "access denied". Yet it stubbornly persists.
Any idea how I can find out what it is, where it came from, and how to get rid of it?
EDIT: Windows 7 x64 Ultimate RTM