Here is a nice post on differences between brains and computers: Developing Intelligence : 10 Important Differences Between Brains and Computers
To make one thing clear: I do not think that artificial intelligence is impossible, on the contrary, I do think that we will be able to develop an artificial intelligence. But paramount to this effort is to get it right, and a lot of AI research is dominated by wrong metaphors (ie software/hardware distinction etc).
Only when we get a clear understanding of how brains work will we be able to develop an artificial brian. Up to now, it was the other way round: we built computers and transferred the mechanisms of computing metaphorically to human brains, ie: memory = hard disk, attention span = ram, thinking = computation, brain = hardware, thoughts = software.
