Non-Poker Related Probability Question

[The Dude]

Here's a simple probability question. And, if you don't mind, can you explain to me how to do this type of problem. Ones like it seem to come up fairly often for me, and I'd like to not have to keep bothering other people for answers. Thanks.

Me and my opponent are playing table tennis. Let's assume that I have exactly a 62% chance of winning any given point. If that is the only information to go on, what is the probability that I will reach 21 points before my opponent? (Let's ignore things like, advantage depending on who's serve it is, win-by-two rule, and such.)