Use the System Restore utility in your Vista operating system to restore an old working software configuration. Click "Start," "Programs," "Accessories," "System Tools," "System Restore." This will correct software conflicts on the computer, restoring it to working order.
Utilize the HP System Recovery tool in your A6700F if the problem refuses to be solved by a simple System Restore. This will restore your computer to its default factory condition, curing everything but the most stubborn hardware issues.
Finally, send the system in for warranty repairs if the problem persists. Your power supply, memory, motherboard or processor is malfunctioning, and the problem can be isolated and found only through testing by HP or your computer retailer.