Project Security / using a form of KEY? [VC#]

Simply put, I want a way to secure my c# project so to require some kind of serial-key/cd-key to any user trying to use it - keep it mind I am an absolute beginner in this field of software development (coding, encoding, encrypting, etc...)
So, I came up with the following scheme:

On launch of the application (when the user double-clicks):
- Check Registry for a value->key X, if found continue and load the application
- If X not found prompt for SERIAL-KEY/CD-KEY
- If valid, add registry value->key X and continue to load the application
- Else abort with error message telling user he needs a valid key

So, right off the bat I wanted to know if anyone see anything wrong with type of security, I know it is extremely basic but I have to start somewhere, of course I am always open to hear suggestions of any kind...

But my actual QUEStION is regarding the SERIAL-KEY/CD-KEY itself, specifically how does one go about generating a "valid serial-key/cd-key"?
I mean, I think I recall reading that VS has a sort of encrypter/decrypter class of somekind but I was unable to find anything and even if I did I doubt it would make any sense initially.

So, I come asking for advice, what route to take, what are the common options, maybe some basic samples/ideas... anything will do, want to start off on the right foot.
Thanks,