probability problem oh shi

You have two coins inside a bag, and you know that one of them is a double headed coin while the other is a normal heads/tails coin. You randomly pick one up from the bag and look at the coin; it's the heads side. You are not permitted to look at the other side of the coin (where's the fun in that?) and instead you have to find out what the chance is that the coin that you are looking at is the two headed coin. So, then, what is the probability?

In b4 half of /sci/ says 1/2

Lol. I was seriously scratchin mah' head for about 10 minutes here. Then I realised I read the question wrong. I thought the question was 'what are the odds that the OTHER coin is double-sided?' Which I'm pretty sure would actually be 1/2, strangely enough ;)