spo12004 0 Newbie Poster

hi,
im new to this site and hope somebody could help me. i have a compaq presario 700 and it is always quitting on me. i tried reformating the HD and got it working for a couple of days. Now it wont even boot. it saying something like " No operating system found". i dont know if my HD is bad cause i use, (Killdisk )on it a data erasing program and it could detect the HD. if somebody has any idea , it will be very much appreciated.
thanks