First locate in your PC the route of your JDK (for instance: C:Program FilesJavajdk1.7.0_45)
then change the JAVA_HOME variable as follows:
Right-click the My Computer icon on your desktop and select Properties
Click the Advanced tab
Click the Environment Variables button
Under System Variables, click New
Enter the variable name as JAVA_HOME
Enter the variable value as the installation path for the Java Development Kit