Unable to download minecraft, please help. I know this isn't a bug - sorry.

What I expected to happen was to be able to download your game after I bought it.
Describe what you thought should happen here

*What actually happened was I am still unable to download it. I have disabled every firewall, antivirus software I know how. I have read all the help files and I have tried to find help online. I have obiviously failed an am desperate for help.
Describe what happened here

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. I have downloaded the installer
3. Then when I trie to run the exe I get the message attached below.
4. Then nothing happens when I click o.k.