Step 1. What's the odds of choosing the right door on your first try? 33%
Step 2. The host eliminates a door and essentially asks you to choose again from 2 doors.
Step 3. What's the odds of choosing the right door? 50%
The whole point of the exercise is to confuse the player and probably get a few giggles out of his indecision. But the matter of the fact is that the game was all about choosing one of two doors.