I am relatively new to Java programming and am getting used to using Eclipse.

I created a project using JRE 1.6 and works successfully. I have both 1.5 and 1.6 JRE and JDK installed on the pc.

Now, I created a new workspace, specified that the Installed JRE's should be 1.5 via the preferences. Copied the previous project into the new workspace and attempted to run as a java application. It gives me the error "Could not find the main class. Program will exit."

I know this is similar to others with this same error but not caused by the same problem of changing JRE versions.

If I change the preferences/installed JRE back to 1.6, it works fine.

How do I get this to run with JRE 1.5? My issue is that different users have either 1.5 or 1.6.

(I also heard that if a java program is compiled with 1.5, it will work on a pc with 1.6. Is this true?)