How to reinstall Oracle XE

Solution based on Oracle XE 11g (it should works for 10g too)
For  Windows

First this is offical guide:
http://docs.oracle.com/cd/B25329_01/doc/install.102/b25143/toc.htm#CIHDDHJD

Good uninstall Guide can be found here:
http://www.oracle-base.com/articles/misc/manual-oracle-uninstall.php

Optional useful tools:

• CCleaner (or any software for clean registry and clean).
• Unlocker (or any software to kill process,that use files)

In the past I've had many problems uninstalling all Oracle prodcts from Windows systems. Here's my last resort method:

• Uninstall all Oracle components using the Oracle Universal Installer (OUI).
• Run regedit.exe and delete the HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE key. This contains registry entires for all Oracle products.
• Delete any references to Oracle services left behind in the following part of the registry (HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/Ora*). It should be pretty obvious which ones relate to Oracle.
• Reboot your machine.
• Delete the "C:\Oracle" directory, or whatever directory is your ORACLE_BASE.
• Delete the "C:\Program Files\Oracle" directory.
• Empty the contents of your "C:\temp" directory.
• Empty your recycle bin.

Installation process is much more complicated as simple next>next>...>finish will end up with troubles.

Follow installation instructions here (but read ONE IMPORTANT NOTE)
http://blog.mclaughlinsoftware.com/2011/09/13/oracle-11g-xe-install/


ONE IMPORTANT NOTE:
You need write down full path as is written on message as full path copied from explorer will not work
The installer is unable to instantiate the file C:\Users\HAPPYUS~1\AppData\Local\Temp\{216DEE42-A1B3-8002-48A2-4A22AE14981}\KEY_XE.reg. The file does not appear to exist

 C:\Users\HappyUser\AppData\Local\Temp\{216DEE42-A1B3-8002-48A2-4A22AE14981}\KEY_XE.reg.

HAPPYUS~1 is OK,  HappyUser is WRONG!


In 75% .It should works,but in some cases it will fails for various bizarre reasons that are beyond my understanding and I didn't find any solution online yet.I hope ,I will not need to deal with this process to often as it is a nightmare experience.

Sources:
http://docs.oracle.com/cd/B25329_01/doc/install.102/b25143/toc.htm
http://blog.mclaughlinsoftware.com/2011/09/13/oracle-11g-xe-install/