It suddenly shut down last night and won't start again. The start button won't do anything, like it has no power at all. But I can get a green light from the back of PSU and all fans runs in full speed as long as I press the BIST (built-in self test) button on the back of the PSU. Is it a motherboard issue? How much should I pay if I want to order one from Dell because my warranty has expired? sad