Cooling Fan Replacement main computer.

I am trying to get into the case of this Toshiba laptop and removing all the screws visible has not allowed me to get it apart. It seems there is something that I am missing in the middle of the laptop and along the side where the CD/DVD rom drive is located that is preventing me from separating the case parts. I have removed the memory and hard drive and see no other parts to remove to get it apart. I have checked the labels to see if there are any hidden screws and there are none. Please help. Thanks.