Re: Can't connect php/4.4.1 to Mysql 5.0.16 : Client does not support authentication protocol requested by server; consider upgrading MySQL client

[Bill Karwin]

I don't think any version of PHP contains the upgraded client. You would have to build PHP from source.

Alternatively, run your MySQL server with the --old-passwords option to let it store passwords compatible with the old MySQL client in PHP.

That could explain why Paul's Linux host seems to work -- it's running with the --old-passwords option already. Use the following statement in mysql to check:

show variables like 'old_passwords';

See this page for more information:
http://dev.mysql.com/doc/refman/5.0/en/old-client.html

Regards,
Bill K.