Another tip-off is aliens that cannot reveal the names of their hard drives. Frequently talks to himself. The alien may be rehearsing or practicing what he will say next. Displays a change of mood when near certain high-tech hardware. An alien may become nervous or hyperventilate when near computer hardware.
Aliens also become unobservant and have trouble reading labels.
If a customer cannot identify the name of the computer, and the name is affixed to the front of the computer, you may have a space alien on your hands.