"A good metaphor is something even the police should keep an eye on." - G.C. Lichtenberg
Although the brain-computer metaphor has served cognitive psychology well, research in cognitive neuroscience has revealed many important differences between brains and computers
Brains are analogue; computers are digital
The brain uses content-addressable memory
The brain is a massively parallel machine; computers are modular and serial
Processing speed is not fixed in the brain; there is no system clock
Short-term memory is not like RAM
No hardware/software distinction can be made with respect to the brain or mind
Synapses are far more complex than electrical logic gates
Unlike computers, processing and memory are performed by the same components in the brain
The brain is a self-organizing system
Bonus Difference: The brain is much, much bigger than any [current] computer
clipped from: scienceblogs.com