fix computer errors

When i turn my computer on…the compaq screen comes up ok….then it says: Disk Boot Failure, Insert system disk and press enter. What does this mean exactly? I didnt have a windows xp disk…so i got one from a friend. My recovery disks wont help either. So when i tried to install windows again…an i get to the part where your suppose to install the windows to my harddrive…it says: unknown drive in the box below. It says that like 5 times in the box below. Then it gives a error blue page. It says: The problem seems to be cause by the following file:setupdd.sys page_fault_in_nonpage_area. What is that exactly? People have told me my harddrive got completely messed up. But others have said it was fixable an the harddrive could be fixed somehow. Is there anything i can do at all to just see if my harddrive is at least ok…or if it can be repaired…without taking it out or anything? Only reply if your a computer pro or may know how i can get my PC started if possible. Thanks.