Oracle is an object-relational database management system for various platforms like Windows and Linux. Installing Oracle Express Edition and creating an initial user is straightforward.
1. Download and Install Oracle Database Express Edition
Beside some Enterprise and other commercial licences (Wikipedia) there is Oracle XE as a free version of the Oracle RDBMS, but it is limited to 11 GB of user data and to 1 GB of database storage.
First go to the Oracle Database Express Edition 11 and download it. You have to accept the license agreement and login with an oracle account. It is up to you to create a new one, maybe register with a trashmail, or using an existing account from bugmenot.
Optional: It may be a good way to install Oracle into a virtual machine by using tools like VirtualBox. This prevents your Windows to slow down, because all database data will load at Windows starts up.
After downloading the zip file, extract is and run the setup.exe file inside the DISK1 folder. In the setup progress you will have to enter a password for the SYS and SYSTEM accounts. Pick a not too easy one, because these are the main admin user accounts of your Oracle Database.
2. Download and Install Oracle SQL Developer
For a graphical interface of the Oracle Database I recommend using Oracle SQL Developer, which only has to be extracted and could be placed directly below your Oracle Database installation, inside C:\oraclex\. For easy use you can create a short cut on your Desktop, which will link to the sqldeveloper.exe.
3. Create a new Oracle Database User
If you connect with the SYSTEM user through SQL Developer to your database, you will see a lot of internal and default tables. To setup a new connection just click green "plus" icon and enter the following information:
Connection Name: system
Password: (the password you entered while installing Oracle Database)
and use the buttons Test, Save and Connect.
Expand the "system" tree, search for Other Users and right-click it and select "Create User. Fill in the necessary information. In the Roles tab check the Granted box for CONNECT and RESOURCE. If you will work with table views you also have to check the System Privileges tab and set the Granted check box at CREATE VIEW.
Now you can connect with the new user.