Photoshop Cs5, I need help URGENTLY!?

okay ao i am doing this class at school which requires me to use the Photoshop cs5 program. I have been using the trial on my LARGE HP laptop but the trial is now up so i downloaded it on my MINI HP laptop but it wont allow me to SAVE AS... and I have tried to change the screen resolution but it still isnt working!!!! Pleaseee HELP!!!! :(