Oracle XE Startup Problem : ORA-01034: ORACLE not available ORA-27101: shared memory realm does not exit | ORA-12631 (Username retrieval failed)

Oracle eXpressEdition a compact and nice to use for development purpose.
But after i installed Oracle XE 11g in my machine it gave me a heavy headache to get it up and run correctly.

Problems i got are as below

• ORA-01034: ORACLE not available ORA-27101: shared memory realm does not exit
• ORA-12631 (Username retrieval failed) 
• http://127.0.0.1:8080/apex/ is not opening
• listener.ora changes does not help
• ....

I was Googling for more than a week for the problems and each solution leads to another problem for example if i solve ORA-27101 then the next gate will be ORA-12631(it goes one..).  

Finally i got relief from the headache.

• To install Oracle XE user should have System Admin privilege.  
  so i got Admin privilege from my network admin.
• I am able to install now, but still it makes problem.
• XE service is not running or oracle Apex is not opening @ http://127.0.0.1:8080/apex/
•  My account is actually networked (Windows NT user).
• I uninstalled XE, then i logged in with the Local System Administrator account (not in NT domain).
• I installed Oracle XE.

Now its up and running oracle Apex is also running well.

So careful, while installing Oracle XE be logged in the system as local Administrator.