Help in watir

I have installed Ruby 1.8.5-21 and also installed the watir gem. but
when i use the below statement
require ‘watir’ #i get the below error

./watir.rb:4: uninitialized constant Watir (NameError)
from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
gem_original_require' from c:/ruby/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:inrequire’
from watir.rb:2

Exit code: 1

please tell me how to prevent this error.

Thanks in Advance
K Sathya Narayanan

how to find element from popup window in wwatir

See this link for an example of how to switch to another window: