rails sqlite adapter error

I'm following the instructions in rails tutorial and got stuck when trying to use the scaffold command.

When running:

rails generate scaffold User name:string email:string  

I get the error:

C:/RailsInstaller/Ruby1.9.2/lib/ruby/gems/1.9.1/gems/activerecord-3.1.0/lib/active_record/connection_adapters/abstract/connection_specification.rb:71:in `rescue in establish_connection': Please install the sqlite3 adapter: `gem install activerecord-sqlite3-adapter` (can't activate sqlite3 (~> 1.3.4), already activated sqlite3-1.3.3-x86-mingw32. Make sure all dependencies are added to Gemfile.) (RuntimeError)

Running:

gem install activerecord-sqlite3-adapter

I got the error:

ERROR:  Could not find a valid gem 'activerecord-sqlite3-adapter' (>= 0) in any repository
ERROR:  Possible alternatives: activerecord-jdbcsqlite3-adapter, activerecord-sqlserver-adapter, activerecord-nulldb-adapter, activerecord-spatialite-adapter, activerecord-simpledb-adapter

My Gemfile looks like this:

source 'http://rubygems.org'
gem 'rails', '3.1.0'  
gem 'sqlite3', '1.3.3'  
...

I'm running on Windows 7 x64 OS.

Any ideas?