I wanna help code mozilla, where do I start?

[Jonathan Wilson]

I know C++ and all that but how do I find something to do?
Also, is there any documentation related to mozilla available anywhere 
so that I know just where to find a particular piece of code in this 
mammoth codebase?
In particular, I am curious to know where the win32 specific code is 
kept (I imagine NSPR would have some and that there would be other bits 
in other places but where is it?)