Laptop overheats, shuts down ! HELP!

Hi I am an aspiring female tech learning the tricks of the trade. My HP Pavilion DV1000 keeps overheating/shutting down. The Internal fans do NOT turn at all causing it to shut down. I have taken the laptop apart and tested the fan itself confiming that it works fine. Where do i go from here? Is it on the motherboard? Is the best thing to do replace the motherboard? I have no warranty so i must fix this myself. Any ideas or advice would be helpful 🙂
FYI,
It is running XP
Thanks!