Register datasource fails with no suitable driver

Aurora #813
windows 2000

When I was trying to register a oracle datasource (jdbc:oracle:thin:...) I could not get past a message:

No suitable driver found.

But I can see that IDEA has found the driver class oracle.jdbc.driver.OracleDriver in my classes12.jar because it does not complain about classnotfound.

Also I do not have classes12.jar in classpath.