Compaq Presario 1245 Help

Question

I do have my old Compaq Presario 1245 loptop and I didn't use it in more then 3 years ,I wanted to restore it to the original factory- installed software state. I just open it and I am getting the following message.Non- System disk errorReplace and strike any key when readyPlease help me on this , I do have the manual with me but I am blank.