Minecraft will not load on my computer even though it is fully downloaded

Put the summary of the bug you're having here
I have downloaded Minecraft but it will not load up, The launcher loads but not the game.
What I expected to happen was...:
I expected the game to load up and I expected to be able to play minecraft.

What actually happened was...:
I loaded the launcher, Pressed play and it crashed and would not load up the game.

Steps to Reproduce:
1. Load up Launcher. ( Minecraft Launcher 1.6.61 )
2. Log in.
3. Press play. After pressing play it crashes.