Error : "Could not find gem 'hpricot', required by 'remit', in any of the sources"

I want to integrate Amazon’s FPS service using remit gem. I have
successfully installed the remit gem but

when I am trying to run server it gives me the following error: “Could
not
find gem ‘hpricot’, required by ‘remit’, in any of the sources”

Installed gems:

1)relax (0.0.7)
2)remit (2.0.1)
3)hpricot (0.8.4 i386-mswin32)

Platform: windows 7 with Rails 3.0.5, Ruby192
I have included the statement " gem ‘remit’ " in my Gemfile.

What should I do?