Oracle 11g XE 64bits installation problem on Windows 7 I had to install Oracle 11g XE on my laptop under Windows 7.
So I follow this Tutorial. The installation didn't even fail once, and seem to be OK.
But every time i tried to connect to it with SQLPLUS, it failed with ORA-12638 error...

SQL&gt; connect
Enter user-name: system
Enter password:
ERROR:
ORA-12638: Credential retrieval failed


After some search I found this Web Site and attempt to resolve my problem with the second solution. But then I get another kind of error : ORA-01034 and ORA-27101...

SQL&gt; connect
Enter user-name: system
Enter password:
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Process ID: 0
Session ID: 0 Serial number: 0


It seem that my database didn't even exist to begin with...
And if looking in [...]\oraclexe\app\oracle\oradata\XE, there is no files.

When looking the logs at [...]\oraclexe\app\oracle\product\11.2.0\server\config\log, I found that during the installation process, the application wasn't even able to connect to the database created.

Example in the file : postDBCreation.log

SQL&gt; connect "SYS"/"&amp;&amp;sysPassword" as SYSDBA
ERROR:
ORA-12638: Credential retrieval failed 
[...]
SQL&gt; startup ;
ORA-12638: Credential retrieval failed
SQL&gt; select 'utl_recomp_begin: ' || to_char(sysdate, 'HH:MI:SS') from dual;
SP2-0640: Not connected
SQL&gt; execute utl_recomp.recomp_serial();
SP2-0640: Not connected


Another file in the same directory : CloneRmanRestore.log

SQL&gt; startup nomount pfile="D:\Applications\oraclexe\app\oracle\product\11.2.0\server\config\scripts\init.ora";
ORA-12638: Credential retrieval failed
SQL&gt; @D:\Applications\oraclexe\app\oracle\product\11.2.0\server\config\scripts\rmanRestoreDatafiles.sql;
SQL&gt; set echo off;
SP2-0640: Not connected
SP2-0640: Not connected
SP2-0640: Not connected
ERROR:
ORA-12638: Credential retrieval failed


I am log as a domain user with administration right on the laptop, so why does the installation fail without putting an explicit error ? And how to ensure that the installation of Oracle 11g XE on my laptop work ?
After more than 6 hours to fix this, I found this post which help me to understand the problem.

The problem was that I tried to install Oracle 11g XE with my user account connected on the enterprise domain. The installation process, then, wasn't able to connect to the database. I suspect that it try to connect to it from the enterprise domain, and not from localhost.

To solve this, I had to redo the installation with a local admin account on the computer and not as an admin user on my enterprise domain.

Found another post for reference.

I hope this answer will help other guy which encounter the same problem.