gem install ruby-serialport gives error

[Sangeeta Huddar]

:::: gem install ruby-serialport
Install required dependency echoe? [Yn] Y
Install required dependency rubyforge? [Yn] Y
Install required dependency highline? [Yn] Y
Building native extensions. This could take a while...
ERROR: While executing gem ... (Gem::Installer::ExtensionBuildError)
ERROR: Failed to build gem native extension.

ruby extconf.rb install ruby-serialport -p
http://proxyin03.itg.ti.com:80
checking for OS... mswin
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:/ruby/lib/ruby/gems/1.8/gems/ruby-serialpor
t-0.7.0 for inspection.
Results logged to
c:/ruby/lib/ruby/gems/1.8/gems/ruby-serialport-0.7.0/ext/gem_m
ake.out


i m facing this problem can anyone help me ??