Here are photos of the process of opening my old Sony VAIO Z505JSK laptop and upgrading the hard drive. The pictures are linked to larger versions.
The pictures on this page should apply to most Sony VAIO Z505 laptop / notebook computers, as well as to the Z600 laptops since they’re the same (just renumbered for the European market). Even where the pictures don’t match, the procedure is the same – carefully disassemble, keeping things organized. If something won’t go, look around to figure out how it might be attached or fastened, don’t just try to force it.
Your laptop was designed to be opened and serviced by technicians without damage. That means there’s a way to get into it without breaking things.
You may not know the official correct steps, but if you think you have to break something then you’re doing something wrong or have missed something. Expect tricky clips and redundancy because of the need to balance between a sturdy laptop and an easily disassembled laptop.