Windows Explorer Locks Up

Hey Guys does anyone have any ideas on this, I tried to move a few avi files into my videos and no everytime i go there it locks up and gives me the error report, Now this happend and I found out it was an avi file however I want to stop this problem altogether so If anyone can Help me I would Be Greatful.

Thanks

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Hello, my nephew watched Mr. Bean in avi format yesterday afternoon. When I arrived last night, strange thing happened. I couldnt sign in to the administrator account! It seemed the pc forgot my pw..I signed in using the guest and tried to delete the file from there but message said I cant! I dont know what to do please help!