After a succesful 10g installation and a dbca assisted db creation, installer complains about "enterprise manager configuration failed ..." and you can retry manually by running emca.
and after you click ok the explorer opens up in a window containing something like that in address bar:
When I explore emconfig.log I saw:
Setting console properties ...
Setting log and trace files locations for Console ...
Setting log and trace files locations for Agent ...
Service "OracleDBConsoleIZMTPRS" create SUCCESS
Service "OracleDBConsoleIZMTPRS" delete SUCCESS
Mar 29, 2010 8:56:15 PM oracle.sysman.emcp.util.PlatformInterface executeCommand
CONFIG: '\regedit.exe' is not recognized as an internal or external command,
operable program or batch file.
Creating registry entries failed. Aborting...
first I checked to see if the windows account which I was using is a local administrator. the account was in a group and the group was under the administrators group. I also added the account directly.
after that I executed: emca -config dbcontrol db
worked like a charm!