Simply Rails 2 2nd edition chapter 11

Installing ruby-debug

I would appreciate help on how to install this gem.

Here's the output I got (rails -v=Rails 2.3.5, Windows XP, ruby console)
Code:
C:\InstantRails\rails_apps\shovell-debug-02>gem install ruby-debug
Building native extensions.  This could take a while...
ERROR:  Error installing ruby-debug:
        ERROR: Failed to build gem native extension.

C:/InstantRails/ruby/bin/ruby.exe extconf.rb
creating Makefile

nmake
'nmake' is not recognized as an internal or external command,
operable program or batch file.


Gem files will remain installed in C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/r
uby-debug-base-0.10.3 for inspection.
Results logged to C:/InstantRails/ruby/lib/ruby/gems/1.8/gems/ruby-debug-base-0.
10.3/ext/gem_make.out