I have 3 of them and the 1st one does not work anymore after 1 year and a half. I have archives on it so it was load and...

Thank you, I finally found a picture of another model with a screw to remove at first, but that gave me the idea to try sliding a rigid plastic card. It is always difficult at first because of the unknown we fear of breaking something, but finally I managed to drag the "U". Now I have to try the HD with another casing... :-)