|If this is a laptop, if it's like a friend's Sony, PCG-FX120, the CD drive is a plug in module - if yours is too, make sure it's module is pushed in all the way, or it won't be recognized by the mboard or the operating system.|
I got no usefull results when I searched with PCG-7Z21, and only a few when I searched with PCG-7Z (e.g. PCG-7Z 29, with a space before 29).
I suspect you either mis-typed the model, or you are using the wrong one.
Many Sony laptops have two model numbers - the one on the label on the outside of it, and another one in the bios. The one stated in the bios is the one you use to search for info or when you specify the model.