It is unclear from your post, are you saying you have installed Windows 7 on C: drive and then it doesn't boot into it because bios is still set boot from usb?
Or do you mean you can't get Windows 7 to install from the usb?
or are you stuck somewhere inbetween the above two scenarios?
You say you have tried most things, but don't say what things.
Is this tutorial any help click here