How do I install a JRE or JDK to run the Android Developer Tools on Windows 7

You can go here to download the Java JRE.

You can go here to download the Java JDK.

After that you need to set up your environmental variables in Windows:

1. Right-click My Computer
2. Click Properties
3. Go to Advanced System Settings
4. Click on the Advanced tab
5. Click on Environment Variables

EDIT: See screenshot for environmental variables