Basic Oracle Concepts and Programming Question:

If StartBD.bat failed to start the XE instance, you need to try to start the instance with other approaches to get detail error messages on why the instance can not be started.

One good approach to start the default instance is to use SQL*Plus. Here is how to use SQL*Plus to start the default instance in a command window:

>cd (OracleXE home directory)
>.instartdb
>.insqlplus
Enter user-name: SYSTEM
Enter password: globalguideline
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist

The first "cd" is to move the current directory the 10g XE home directory. The second command ".instartdb" is to make sure the TNS listener is running. The third command ".insqlplus" launches SQL*Plus. The error message "ORA-27101" tells you that there is a memory problem with the default instance.

So you can not use the normal login process to the server without a good instance. See other tips on how to log into a server without any instance.