Error in ROR App on running code

hi all ,
I am getting error when i try to run my app. from Radrails, also when installing “gem install ruby-gd” it shows some error,
Can anyone provide the right installation steps and libraries name which required to install gd libraries ?
thanks in advanced …

D:/Ruby187/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require': no such file to load -- GD (LoadError) from D:/Ruby187/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in require’
from D:/Documents and Settings/Administrator/My Documents/Aptana RadRails Workspace/suggestica/config/…/lib/captcha_image.rb:22
from D:/Ruby187/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' from D:/Ruby187/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in require’
from D:/Documents and Settings/Administrator/My Documents/Aptana RadRails Workspace/suggestica/config/environment.rb:24
from D:/Ruby187/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in gem_original_require' from D:/Ruby187/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in require’
from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/…/lib/mongrel/rails.rb:147:in rails' from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/mongrel_rails:113:in cloaker_’
from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/…/lib/mongrel/configurator.rb:149:in call' from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/../lib/mongrel/configurator.rb:149:in listener’
from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/mongrel_rails:99:in cloaker_' from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/../lib/mongrel/configurator.rb:50:in call’
from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/…/lib/mongrel/configurator.rb:50:in initialize' from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/mongrel_rails:84:in new’
from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/mongrel_rails:84:in run' from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/../lib/mongrel/command.rb:212:in run’
from D:/Ruby187/lib/ruby/gems/1.8/gems/mongrel-1.1.5-x86-mswin32-60/bin/mongrel_rails:281
from D:\Ruby187\bin\mongrel_rails:19:in load' from D:\Ruby187\bin\mongrel_rails:19 from -e:2:in load’
from -e:2

Thanks and Regards
Sachin S. Kewale