best open source c++ compiler

You are comparing apples and oranges. Visual C++ Express 2008 is an IDE (Integrated Development Environment) and that's way more than a compiler as gcc is. Stay with VC++E2k8 as it is the most comfortable development environment for C++ in my opinion. For Java development I recommend Eclipse.

He said he want a open source compiler.
First of all, Congratulations for choosing Open Source.
G++ is accepted as the most widely used open source compiler. You can use it on M$ Windows too.
MinGW is just a port of G++ for M$ windows. Both are nearly same thing.
You can use CodeBlocks as your IDE. Codeblocks is also free and it support g++/MinGW.
I have listed few of the compilers for M$ windows here :http://siddhant3s.googlepages.com/how_to_tell_rusted_cpp.html#SECTION00041000000000000000

<noflame> MSVC++ is not a open source compiler. It is not a free compiler. It is a compiler which comes at zero cost. There is no reason that VC++ is more compiler than what gcc is. G++ is the standard compiler for most of the Linux platform. There are far more developers using g++. It is more free than MSVC++ is and every would be. Moreover MSVC++ is not available on any other platform else MS Windows. :( . So keep your "more a compiler than gcc" remark with you when you have not used/ or used g++ even once.
</noflame>

You are comparing apples and oranges. Visual C++ Express 2008 is an IDE (Integrated Development Environment) and that's way more than a compiler as gcc is. Stay with VC++E2k8 as it is the most comfortable development environment for C++ in my opinion. For Java development I recommend Eclipse.

Well I'm not exactly comparing anything but to make it clearer, I am trying to modify a compiler to compile my own type of applications. And the overall project is being done is Visual c++ Express 2008. So I hope that makes more sense and download links with 1 or 2 tutorials on compiling would be good.