When I try to start playing minecraft it says theres a crash, i have redownloaded it and everything. Nothings working! What do i do!?!??!

Put the summary of the bug you're having here

What I expected to happen was...:
I thought i was just going to be able to redownload it but.. no

What actually happened was...:
It wont let me even get to the game.. redownloading it doesnt work.

Steps to Reproduce:
1. Start minecraft
2. Hit Play
3. Then the crash happened.