When you're asking for help, remember: details, details, details. It's important to list all the pertinent details of the problem you're encountering or people have no idea how to help you. Not all Vaio machines are created equal -- what model of Sony do you have?
Most computer cases open with one or two thumbscrews on the rear of the case, after which you can slide off the housing, but your best bet is to go here http://esupport.sony.com/perl/select-syste...DOCS&PRODTYPE=1
Find your model of Vaio and see if you can find some documentation.
Now before you go mucking around inside the computer case, make sure you know what you're doing *or* make sure you have good medical insurance and don't care if you destroy the computer. Before you open the case, make sure to unplug the computer and then make sure you discharge any static electricity that may have built up on your person. Touching a grounded metal object (like a waterpipe that goes into the ground) is usually enough to get rid of static, but remember, just walking back to your machine can build up more static. An anti-static wrist strap is what most people use.
Sorry if any of this sounds condescending. I'm just trying to warn you from getting in too much over your head.