It depends what you mean by "think". If you mean simulate conscious itelligent behaviour then the answer is "yes".
If you mean "can a computer be or become conscious" then I would argue "NO" because it is impossible to say how consciousness can arise from the action of unconscious processes.
I recently wrote a Hub on the theory of the brain as a filter for universal consciousness that took consciousness as an irreducible primary aspect of the universe line space-time and energy. If this theory corresponds to reality then it might be possible to create a computer that is conscious.
In a trivial sense a contemporary computer can only do what it is programmed to do. It is possible to write self modifying programs and then in a sense the computer does things it was not originally programmed to do, especially if the changes are dictated by external inputs.
The bottom line is that the word "Think" is ambiguous and the question is actually two questions. I personally think Intelligence does not require consciousness but consciousness requires intelligence.