When someone is seeing problems like even getting to the post screen often a board is pulled out with only the basics being cpu, memory, video card, monitor, and supply to see the board will at least post and to make sure no standoffs were in the wrong place grounding the board out. This is also done with an older build now seeing problems as a way to isolate a bad card, cpu, or memory.
Most of the time this is simply a method for diagnosing problems rather trying to run a new board outside and trying to get eveything installed like OS, drivers, softwares. Here I simply wait until I get everything together before the first run in order to double check all connections to make sure things are plugged in and no wires from the power button, p led, hd led are crossed.
Once a new build posts like it should the OS and other things go on at that time. You may think everything is all set while outside of the case but then wonder why you have problems once the board is in from reversed wires, one plug not in, or something touching and end up scratching your head trying to figure out why it won't run then.