New to Java

I am a total newbie to Java. I have successfully run the usual "HelloWorld" program, but am having trouble using jars.

I have the following on my C:drive under the Program Files Folder:
Java, under which is jdk1.6.0_20, under which is lib, under which is acm.jar.
Program Files
Java
jdk1.6.0_20
lib
acm.jar

I have set the system variable CLASSPATH to: C:\Program Files\Java\jdk1.6.0_20\lib
I have set the user variable Java to: C:\Program Files\Java\jdk1.6.0_20\bin

I am trying to compile the program BouncingBall.java (stored at C:\Documents and Settings\Owner\My Documents\Temp) which includes these lines:
import acm.program.*;
import acm.graphics.*;

At the command prompt C:\Documents and Settings\Owner\My Documents\Temp
I have tried:
javac -classpath acm.jar BouncingBall.java
and simply:
javac BouncingBall.java

Both these attempts give me a long list of errors of the type "BouncingBall.java:11: class, interface, or enum expected"

Can someone please help me get on the right path here? Thank you.