I think that happened to me at one time too. I'm not sure whether it was with my external drive or with a flash drive, but I remember having to do the Device Manager "fix" described in the video.
On another WIN 7 machine I use, there are 5 or 6 Removable Discs that show up whenever I click Computer (I only have 1 external drive plugged in). They all pop up a message like "Insert a disc" or something...
Windows is weird sometimes...remember when dealing with Windows that it makes mistakes, gets itself in an endless loop of some sort or it drops a 1 byte or a 0 bit in its own address paths every once in a while...
Ever since the 1st operating system came out and still to this day, Windows requires a reboot to fix things. I compiled a list of some the stuff that has frustrated me over the years--->Weird Windows Stuff