Mysql.so errors with MySQL 5.0.77

I have updated Rails to 2.2.2 and then found I had to update MySQL to
work with the mysql gem. However, I’ve found that with MySQL 5.0.77, I
get this error:

LoadError (126: The specified module could not be found. -
c:/ruby/lib/ruby/gems/1.8/gems/mysql-2.7.3-x86-mswin32/ext/mysql.so)

Google search suggested removing the mysql.so but that didn’t fix the
problem. However, downgrading MySQL to version 5.0.18 (the version I had
running on a development PC that wasn’t getting an error) fixed the
problem.

Another thread:

http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/55dd057c41a72fc5

Suggests problems with MySQL 5.0.27. It looks to me that the mysql gem
on Windows systems is very dependant on MySQL version.

OS Windows 2003 server.