Interviewed here:
I'm an amiable, low-voltage atheist.
RCR: Does that present a problem for you as a conservative?
GW: No. The Republican Party's base is largely religious. It would be impossible for me to run for high office as a Republican. Since I have no desire to run for office, it's a minor inconvenience! I think William F. Buckley put it well when he said that a conservative need not be religious, but he cannot despise religion. Russell Kirk never quite fathomed this, which is one of the reasons why I'm not a big fan of The Conservative Mind. For him, conservatism without religion is meaningless.