Or it could still be the mobo...
Basing a lot of the features off of mine, probably has quite a few less features but I can't look his board up right now so I am just going to wing it off memory.
The memory he has is supported, so unless it's a faulty dimm or dimm slot, the go button should resolve any memory issue upon power up. But, if it is the memory, the board should still power on and throw a debug led number.
If it's the CPU, there should be a debug led number and not sure if the maximus formula has a cpu light or not, but if it's faulty there would be a red led.
If it's the GPU, should still post, just wouldn't be a pic. But he should still test without the GPU installed, he has the luxury of using onboard video, so use the IGP.
Can boot without a hard drive, not an issue.
The only thing that should be an issue (if it's not the mobo) is the power connections or a faulty psu.
It could also be as simple as him having the power switch on wrong and the lights he's seeing are just the leds showing the board is getting power