I KNOW most of you have had customers like this.

Customer baught some ram, and can't get it to work. Brings it back, we put it on a bench system, and it works like a champ.
He takes it back and still can't get it working. We ask him to bring his computer in, and he says "I'm an MCSE, I know what I'm doing."

2 days later he brings his computer in, and what it was, he wasn't pushing the DIMM all the way down.

Thanks to flashcards, and good books, this kind of thing is becomming more common.