Oracle provides all the installation requirements for each version of oracle in their online documentation library which is available on the www.oracle.com website.

Before you plan an Oracle Database Software Installation for a particular release and for the different platforms (Windows, Solaris, Linux, AIX ). You will go to the oracle website, download and review the oracle documentation for that release and create a document including the oracle install requirements which you will use as a guide to ensure that the Oracle servers are properly set up for your installation.

• Follow the link to download Oracle 11g R2 Oracle Technology Network.
• You will be required to create an account with oracle before you can download the software. You account is free (Oracle has made the software available to individuals for free for learning purposes but businesses are required to pay a licensing fee in order to get support).
• You need to install both an Oracle database Enterprise Edition and the Oracle client.
• I recommend that you install the Oracle SQL Developer client as well.

For the Oracle server, I recommend the Oracle 11g R2 Enterprise Edition. Oracle supports 32 bit and 64 bit versions of Oracle 11g. Check if your windows computer is a 32 bit or 64 bit .

Note :A 64-bit windows operating system can support either a 32-bit database or a 64-bit database. A 32-bit operating system cannot support a 64-bit database. So, version identification of the OS is necessary prior to install oracle.

The biggest difference between 32-bit and 64-bit OSes is that the 32-bit version can only address a bit less than 4GB of memory, in total, for the entire system.

Installation involves the normal tasks of downloading, copying files, setting up registry items, and so on. The last part of the installation is configuration of a default local database.

Follow the link to the oracle database 11gR2 installation guide for windows

Oracle Online Documentation For Oracle Database 11gR2 Installation Guide For Windows