1) Install Ruby on Rails
2) do "gem install mysql"
3) Install the MySQL server version of your choise
4) Don't copy the libmysql.dll from your mysql dir to your ruby/bin dir.
Copy the libmysql.dll fromĀ
http://instantrails.rubyforge.org/svn/trunk/InstantRails-win/InstantRails/mysql/bin/
to your ruby/bin dir.
5) start programming in RoR