Question

Windows Vista, Ruby v. 3.3.5

C:\>gem install rmagick

Building native extensions.  This could take a while...

ERROR:  Error installing rmagick:
        ERROR: Failed to build gem native extension.

C:/Ruby19/bin/ruby.exe extconf.rb
checking for Ruby version >= 1.8.5... yes
Invalid drive specification.
Unable to get ImageMagick version
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
        --with-opt-dir
        --without-opt-dir
        --with-opt-include
        --without-opt-include=${opt-dir}/include
        --with-opt-lib
        --without-opt-lib=${opt-dir}/lib
        --with-make-prog
        --without-make-prog
        --srcdir=.
        --curdir
        --ruby=C:/Ruby19/bin/ruby


Gem files will remain installed in C:/Ruby19/lib/ruby/gems/1.9.1/gems/rmagick-2.
12.2 for inspection.
Results logged to C:/Ruby19/lib/ruby/gems/1.9.1/gems/rmagick-2.12.2/ext/RMagick/
gem_make.out

Answer 1

On Windows, you should use the rmagick-win32 gem.

http://rmagick.rubyforge.org/install-faq.html#win