How to run Techtool:

• If the machine is turned on, turn it off.
• Netboot the machine.
• Once netbooted look for the yellow icon on the dock that has a picture of a screwdriver.
• 
• Click on this icon to open techtool.
• If you suspect a hardware malfunction then it would be best to run the hardware test.
• Click on the second tab on the top of the program labelled "Tests."
• Then make sure that the hardware icon is highlighted under the main tabs.
• Click the play button next to the word Hardware to begin the test.
• This test will report if there is anything wrong with your machine's hardware.
• If you are unsure of what is wrong with your computer then you need to run one of the suites.
• Highlight the "Suites" tab on the top of the program.
• Click the play button next to the advanced test and let it run.
• This suite will test all aspects of the computer and let you know whether it is hardware that is malfunctioning or software.
• If the hardware is faulty the machine will need to be sent out to Apple.
• If the software is faulty then the best thing to do it run DiskUtility and DiskWarrior to try and correct the problem.