Wow, you can write a Peer-to-peer program? You say you're only 13? Amazing...
Hope you can take the complaints and responsibility the people will be throwing at you when they try to sue you...remember the case of the US versus Groekster? How about Napster?
Anyway, back to your question: It depends on what you call easy...I myself know the book you're talking about (written by James Foxall, right?), and I am already at hour 11. Yes, basically, VB2005 is easy, if you have a good book to teach you.
Is VB2005 going to be fun? Not all the time...Case in point, I did not have fun when I was trying to figure out what syntaxes, DLLs and SDKs I need just to run a voice recognition program...In my opinion, it's fun when you know what you're doing and what you're gonna do, but not fun when you don't know where to start...
Bottom line is: If you wanna help people by writing Windows-based applications, and if this is enjoyable, then go right ahead, by all means.
However, if you want to challenge yourself, and see how much comprehension you can take at your age, then try programming in Java or C++. These 2 are good foundation ProLans, as you'll easily understand the concept of Object-Oriented Programming.