No offence to your friend but this is why some people should just buy a pre built machine.
Building a PC really isn't as easy as it sounds. Just the other day on here we had a dude trying to screw his motherboard straight to the tray with no standoffs and I saw at least two instances of that when running a shop.
The problem is that no case I have ever come across has any instructions on building a PC. I mean, there simply aren't any. You could probably buy a book though.
I've seen far worse than that though. I remember once some guy came in and wanted to buy a CDRW drive (back in the days when burn proof very first came out on SCSI drives). He point blank refused to pay £27.50 to have us do it and asked me what to do.
"I dunno man, I guess just connect every cable". Yeah, right.
He found a 2 pin 12v cable on the psu and jammed it onto the master jumper pin on the drive. Simultaenously burning the entire PC. So bad was it that the IDE cables burnt so that all that was remaining were hair like wires with no coating on them at all.
He did see the funny side though. But didn't when he had to pay £600 for a new computer.
Even my friend who has built three PCs made the fatal mistake of forgetting to plug in the 8 pin. And that cost him his Phenom 9950 (sent it to me confident it was dead).
Crazy really. I guess people who know things automatically assume that some one else can pick them up in five minutes. And there are just sooo many mistakes to be made when fitting stuff.
Ah well, sounds like you did him right in the end