access to registry

Hello!
May you give me an example for access to the registry?
I need to read and write two files.
one for the demo (30 minus one for use)
and
one to know if it is the full version or not.
i've downloaded reg.decls and reg.dll from this website.
thanks

browse the code archives .. there's registry stuff in there.. (don't ask me how it works tho, never used it)