Hi
To use RMagick you need to have ImageMagick or GraphicsMagick installed.
All you need a c compiler to compile the extension natively. This
involves installing Mingw to get gcc on Windows - or if you have access
to MS Visual Studio/ MS Visual C++.
Either that or you download and install the RMagick-win32 gem, see:
http://rmagick.rubyforge.org/install-faq.html#gcc
Follow the link for installation instructions.
HTH
Clive