Do you want communicate Arduino through PC? You come to right place.
I developed a small program that allow you insert letter 'a' and receive letter 'b'.
You will need install Visual Basic 2008 and Arduino environment. With Arduino environment, copy the code source from the next image.
Finally, copy the next code source to Visual Basic 2008 from the next images.
The User Interface (UI) is something like this:
You can see the communication between PC and Arduino. Just click here!