To become an actuary one must pass several examinations. The first set of exams are mathematically intensive and the second set are based on the theory of investments, actuarial science, pensions, and other such topics. However it will be difficult to find employment without a college degree. Most actuaries have at least an MA in mathematics. Your Microsoft certification would certainly give you bonus points but not enough to compensate for a lack of a degree. To learn more visit the Society of Actuaries web site.
Update: Since this question was posted the Society of Actuaries changed the exam requirements. There are now fewer but harder exams. That is about all I know about it.