i find its much easier to install graphics cards, memory etc if its laying down and those pesky little front
panel connectors for power , reset etc
i should have said can even lay it on its side when its on--but turn it off first then lay it down before
turning it back on--and not with the heatsink hanging downwards
reasons for turning it on laying it on its side
cant fit under the desk standing up
trouble shooting--ie remove one memory module power back up--need to remove another memory module and so forth checking all fans are spinning properly etc
obviously if its powered up use common sense
no drinks, pets , children etc