Hello Avinash,

to hide a method, select it in the IDE, click on Tools, Procedure
Attributes, click on Advanced and check "Hide this member".
As I said, this hides the member from the Object Browser and
the intelli sense, but not for any tools the reads the type library
(like OleView). I use it only to make a method obsolete without 
deleting itand and breaking compatibility.

As for an activation key, to make it bullet proof is not that easy.
Any hacker can disassembly the code and find where the key is
stored. But there are third party components that can do this job,
as usually take the best you can afford.

Marco