Attempt to launch it as with administrator privileges. Right click run as administrator If this doesn't work then delete your.minecraft folder. To find this press the windows + r button at the same time. This will bring up the run menu. In here type ℅appdata℅ and run it. The.minecraft folder should be at the top.
Upon purchase, you'll receive a download code which you'll redeem directly on your console or online through your console's website. Codes are typically delivered instantly, but may take up to five hours in rare cases. This code will be stored on Your Games Library on Amazon if you need to access it later.
Open it up and delete its contents. This will destroy your saved data ( although you can back that up).
After this has been deleted reinstall minecraft and restart your computer. To back up your saves for example simply just copy the world folder to your desktop and then add it back into your new installation when you want to access them again. DO IT NOW BISH.