For starters, that CPU doesn't support the game.
Secondly, why on earth would you set the Steam Library inside of your own root user folder? That is going to cause permission issues.
Other things like not excluding the client from security software could cause this. Or something like setting a custom pagefile in Windows.
After you exclude the client from security software, you will need to validate the files a few times. (How to exclude is covered in the Pinned Support FAQ thread. It's above the Pinned thread on how to report an issue that you skipped over.)