LoadError using MySQL with ruby (mysql_api.so not found)

I installed MySQL 5.5 ( mysql-installer-5.5.15.0.msi ) and mysql gem ( with "gem install mysql" command ) . Now I write a simple program and when I run it ruby give me this message :

C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': 126: The    specified module could not be found.   - C:/Ruby192/lib/ruby/gems/1.9.1/gems/mysql-2.8.1-x86-mingw32/lib/1.9/mysql_api.so (LoadError)

can someone help me to solve this problem? thanks

I copied "libmySQL.dll" file from 'C:\Program Files\MySQL\MySQL Server 5开发者_StackOverflow.1\bin' to 'C:\Ruby192\bin' but now when I run a program Ruby give me this error :

C:/Ruby192/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require': 193: %1 is not a valid Win32 application.   - C:/Ruby192/lib/ruby/gems/1.9.1/gems/mysql-2.8.1-x86-mingw32/lib/1.9/mysql_api.so (LoadError)

http://instantrails.rubyforge.org/svn/trunk/InstantRails-win/InstantRails/mysql/bin/ You have to use the libmysql.dll here to resolve the problem.