The issue that causes "Error MSB3073 exited with code 3" happens to be with the VALUE in the Outputs property under Project > Properties > Configuration Properties > Custom Build Step.

When I choose Edit for Outputs, a dialog box comes up.  I enter a value of "$(OutDir)\regsvr32.trg" in the upper textbox then click OK.  Now for some reason VS 2010 changes the display text to show "$(OutDir)\regsvr32.trg;%(Outputs)".  I'm not sure why or if that is the cause of the problem.

However, I will get "Build Successful" if I change my Output value to "<inherit from parent or project defaults>" instead of choosing Edit and putting a value in.  No more Error MSB3073 exited with code 3.

I guess I can say this issue is resolved but I'd like to know why/what causes this issue to begin with.