Question : Netbeans cannot find main Class

Hi Experts
I have a project in Netbeans 6.5. Which works great. I created a copy of this and renamed.
On a different computer, I installed the latest Java 1.6 and Latest netbeans 6.7.1.
Everything compiles and builds ok but When I run it through netbeans. It says Main Class not found. IF I create a new project in the new versions of Netbeans, it runs ok.
Any clue to why this is happening?
thanks

Answer : Netbeans cannot find main Class

check your run configuration in the new project