I have downloaded and installed IDEA 13.1. However, even having a 64-bit system, Windows has automatically installed the program in the folder Program Files (x86)
In C:\Program Files (x86)\JetBrains\${Intellij Idea version}\bin, there is an executable called idea64.exe. This is for 64-bit systems. You can simply change your IntelliJ shortcut path to it.
You also need to add a new environment variable IDEA_JDK_64 pointing to your 64-bit JDK so IntelliJ can use a 64-bit JDK.
idea64.exe uses this JDK search sequence:
IDEA_JDK_64 environment variable..\jre64 directoryJDK_HOME environment variableJAVA_HOME environment variableMore can be found in a related IntelliJ support article.