There are two screws that need to be removed to access the hard drive on the bottom of my Sony vaio vpcee41fx laptop. One of them is easily removed with a Phillips screw driver but I'm having trouble finding a screw driver to remove the other one. The other screw has what appears to be a circular indentation on the top of it. What type of screw driver do I need to remove this screw? Thanks in advance for any help.