Need help setting up Eclipse + JDK 6

I just started to study java by myself and installed eclipse + jdk6 to run some examples of my book. The problem is: I can't run anything on eclipse. When I try to run the project I get an "Unable to Launch" error. Here's a screenshot: http://img242.imageshack.us/img242/8885/eclipseerrorpx1.png

Checking the java version I get this:

java version "1.6.0_10"
Java(TM) SE Runtime Environment (build 1.6.0_10-b33)
Java HotSpot(TM) Client VM (build 11.0-b15, mixed mode, sharing)

Also, I installed Netbeans, and it works fine (openjdk).

Thanks in advance.

How are you trying to run it? Are you clicking on the run button?

Try this, right click on the project (or on the file with the main() method), click on "Run As" and run it as a Java Application.