I wanted to install PHP Composer in Windows. And to begin, I already have a copy of XAMPP 1.8.1, I think if you have a different way to get your PHP that should not matter. I tested this to work for Windows 7 but it should work for all versions of Windows.
0. Download and install XAMPP
You can download XAMPP here. I got the 7zip version rather than the installer itself. The ZIP version is similar, just with a larger file size. I extract the xampp folder into my C: drive, i.e. to C:\xampp. Then install it by opening the file C:\xampp\setup_xampp.bat. That will set the paths in XAMPP’s configurations.