You may need to delete and readd the service.

oradim -delete -sid testsid

oradim -new -sid testsid -SRVC OracleServiceTestSid -PFile d:\oracle\ora90\database\pwdtestsid.ora -startmode a

You may also want to look at the registry local machine\software\oracle

Look to make sure that the path to the file is correct.

If all else fails reboot and then see if oracle is running.