Change database files location in MySQL administrator?

I would like to change the database files location of MySQL administrator to another drive of my computer. (I run Windows XP SP2 and MySQL Administrator 1.2.8.)

--Under the startup variable --> General Parameters --> I changed Data directory: from C:/Program Files/MySQL/MySQL Server 5.0/data to D:/....., but after I stopped the service and restarted it, the following error appeared:

Could not re-connect to the MySQL Server.
Server could not be started.

Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist

Has anyone else had this problem?