ERROR in nios project build up

Hi

I am trying to emulate an ip core usinf fpga stratixIII board.The emulation checkup i am trying to do with the niosII ide tool.My project includes implementation of multiple cpus.So naturally i included the n number of projects and also the necessary c files and header files required for each of the project.But i am incurring the following error during the project build up.

The proejct <directory name> has no design files.

Please help me out.

Thanks

Nksom