There seems to be a host of things that can cause this error message so you might have to be patient whilst we try a few things! I`ve checked out several forums for this problem and I`ll try to use the most common things that cured the problem.......
Do you get this message when you start in safe mode? (Tap F8 key repeatedly on boot up to enter safe mode)
Do you have, or used to have, Norton, Quicktime or iTunes installed on your system?
Finally for now, Do you have a card reader?