I cannot get the back off my acer computer to

Look for a plastic screw cover at the top part of the table stand. You will have to use a plastic pry bar or plastic putty knife to unlock the inside holding clips. This procedure will have to be repeated when you remove all the screws from the rear panel to unlock the rear plastic casing from the front panel casing. Be careful not to apply to much pressure or you may break the plastic locks that hold together the case. Hope this helps you with your problem.