Get your self an freezer bag from your fridge and place a towel around it. Then try booting your computer. If it is a cooling problem, the computer will continue to run. If the thermal connectivity has failed in the chip, the computer will freeze up after 8 to 10 minutes. Now you will be able to see if you have a heat problem or a motherboard problem. iBooks are known to have chip failure. The thermal conductivity between the layers comes unglued and renders the computer junk. Unless you can preform heat sink surgery. using heat sink extreme heating. Go to youtube and search for iBook repairing of chip on an iBook.