So long story short a guy and his friend build a PC for the first time after I list them the part for the birthday of another guy. They build the thing and when they get to switch the PSU on to try it one of the HDD start to burn, probably pretty strongly since they unplug the computer in less then 5 sec but got all the parts covered in smoke. I ask and the flame looked like ones you would get from burning wood but since it was a brand new HDD it can't be dust and the paper wouldn't make enough smoke to cover everything in the time frame. Also they check afterward and they didn't made a mistake, it the part that was "faulty".
I'd just like to know how the heck can a hard drive catch fire like that because the only time I've heard of something like that are from the NSA server that were sabotaged?