Keeps on crashing on start

Put the summary of the bug you're having here

What I expected to happen was...:
Minecraft would take a while to load

What actually happened was...:
I was pressing the button to play minecraft it disappeared (the tab) then said it crashed
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2go on Minecraft (2).exe
3. ...press play demo date 10/6/13