If…
1. You installed Oracle XE but you cannot launch APEX or start up oracle.exe process
2. Your computer joined Windows domain
3. You installed it using Domain account
Very likely, it will try to install it using domain authentication which it may not work.
Therefore, the solution is to:
1. Create a local user with admin right
2. Log in using that local user and set regional setting to en-US
3. Install Oracle XE
4. Go to c:\Oracle\app\oracle\product\10.2.0\server\NETWORK\ADMIN\sqlnet.ora and remove the line that said SQLNET.AUTHENTICATION_SERVICES = (NTS)