Dell Inspiron Laptop powers on in Power Management Mode

I have a Dell Inspiron 5150 Laptop that appears to go into Power Management Mode when powering it on. When the power button is press the power light comes on, the fan starts for a second then stops and the power light goes out then flashes. No display no other lights.
I have tried removing the battery & conecting to mains power, still the same. I have removed the RAM and HDD still the same.

It has had HDD problems for last few months have have been able to get it to power on and boot from CD to restore the HDD problems.

Is there a way to get it to power on.

Thanks
Sydney