Removing hard drive from Compaq Presario 5630

I want to remove the hard drive from my Compaq Presario 5630 before
taking the CPU to the dump. I have opened the case and the Bigfoot hard
drive is firmly attached to the right hand side of the chassis. There
are nine small screws visible from the interior, none of which I have
yet been able to unscrew. There are two small screws visible from the
exterior, neither of which I have yet been able to turn. There also
appears to be some kind of largish keyhole/post arrangement partially
concealed by the front flange of the chassis. I only want to make sure
no-one can access data on the reformatted hard drive.

Can someone tell me how to remove the drive?