Dear Ramya,
Thank you for your interest in OptiGrating. The trial version is fully functional for 30 days.
I would suggest copying the samples to another directory and verifying that you have indeed permission to modify and save design files. By default, they are installed in root directory and often users might have restricted access to C drive on office/university computers.
If the issue persists, please provide your windows version and we will try to emulate the setup environment.
Kind regards,
Amin