Java 1.7 installation on windows will include downloading couple of executable binaries , JDK (Java Development Kit) and JRE (Java Run time Environment) and setting few environment variables.
1.Download JDK 1.7 and JRE 1.7
Download appropriate version of JDK and JRE for your windows. choose appropriate version based on your operating system, If your operating system is 32 bit download 32-bit version of Java 1.7 and it is 64 bit then download the same. Make sure you downloaded related JRE for selected JDK to Java 1.7 installation.
Download Link : Java 1.7 on Oracle
2. Setting Environment Variables
You would actually need to set below environment variables for Java 1.7 installation and configuration on windows.
Set the JAVA_HOME to JDK installation path. If your JDK is installed in C:\Program Files\Java\ then set JAVA_HOME to C:\Program Files\Java\jdk1.7.0_45
JAVA_HOME : C:\Program Files\Java\jdk1.7.0_45
Set Path variable to know windows operating system about your Java 1.7 Installation. Append your Path to existing Path variable using %Path%; otherwise your other installations will be corrupted.
Path : JAVA_HOME\bin;%Path%;
Set ClassPath to get the availability of Java libraries (rt.jar and i18n.jar) to application environment. These jars are available in C:\Program Files\Java\jre7\lib so set ClassPath variable to this location.
ClassPath : C:\Program Files\Java\jre7\lib
3.Verifying Java Installation.
Open command prompt and type commands in the screen shot to verify the environment.