Strange problem with Win 7

I insert a DVD and go into explorer and click on DVD to open it. At this point the green search bar at the top of the explorer starts to fill as though I have requested a search. The search field top right says "search c:" (or my documents or my computer on different tries) but is otherwise blank. I haven't requested any search. The green bar fills to 75% in a couple of seconds, 99% within a couple of minutes and then it sticks (there has been no visible movement for several hours).

I have tried it a few times with different DVDs and CDs and the same thing always happens. Any ideas

Thanks for your help