Solving the entire game tree for chess is impossible, or rather cannot be done in less time than the currently accepted age of the universe. This was explained to me in college by a pretty smart professor, and I'll try and see if I can simulate his numbers...or better yet, look it up on Wikipedia:
http://en.wikipedia.org/wiki/Shannon_number
Basically, there are 10^80 or so atoms in the universe, and the game tree for chess has around 10^120 possibilities. If you converted every atom in the universe to a supercomputer, each would have to solve 10^40 combinations. If it could perform 10^15 combinations per second, you would still need 10^25 seconds to solve chess. 10^25 seconds is 3.17 * 10^17 years. The universe is only about 10,000,000,000 (10^9) years old, so we're still off by a factor of a billion or so.