the same happened to me at my grandparents when i downloaded something check if u have any other downloads on the comp before downloading scratch it messed up the screen like what happened 2 you when i did that make sure there is nothing slowing down the comp or something
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Your computer may be overloaded or a file may be corrupted.
Try restarting your computer and running it as an administrator.
Then try redownloading to an empty directory and running the installer with no other programs running at the same time.
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Just try diwnloading again and have no other programs open.
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