Do you get a message that looks like this?
Error: cannot access javax.swing.JFrame
bad class file: C:\Program Files\Java\jre1.5.0\lib\rt.jar(javax/swing/JFrame.class)
class file has wrong version 49.0, should be 48.0
Please remove or make sure it appears in the correct subdirectory of the classpath.
It may mean that your computer has two different systems on it and is an inconsistent state. If your computer has jre5.0, then it cannot use SDK 4.7. Uninstall SDK4.7 and download JDK 5.0 and use its tools.jar