Try starting without the battery, Then remove the memory, and try starting with each chip one at a time in each slot. Many time this is either a bad battery or a bad memory chip. Also check the power supply with an ohm meter for the proper output. If the supply checks good, and the other two suggestions don't work, then the problem will most likely be with the power management system on the motherboard. If this is the case, then you will either need to have the exact motherboard component traced by a tech, or replace the motherboard.