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i know this sounds silly but have you turned it completely off and turned it on again. sometimes the win 7 doesnt load properly when first loaded but after restarting the computer it will start working.
i will put up an offer for the phone call if you like but you might want to look at this first
if you can get to the settings by right clicking on the start menu and selecting settings
you can then select system and recovery
that has some repair options including the ability to put it back to windows 7
if you cant get there you need a win 10 boot disk
you can reinstall the software from a flash drive using the instructions from this pagehttp://www.cnet.com/how-to/how-to-install-windows-10-technical-preview-from-a-flash-drive/you can get the actual iso download to use to make the flash drive on this pagehttps://www.microsoft.com/en-us/software-download/windows10using that flash drive you can re install the entire operating system.
than you will have to go the boot disk method.
this page lets you download a program that will create a bootable flash drive with windows 10 on it.
make sure that you select the method for instaliing on another machine. and you would have to use another computer to create the flash drive. i am sorry but there is just no other way to do it other than setting the computer back to the windows version it originally came with in factory condition with everything else wiped out.