Solved! windows deleted can't reinstall

[pedrobird]

i purchased Asus T100TA from new running windows 8, a couple of years ago i updated to the free windows 10 upgrade without any problems.
Due to a lack of space on these machines i deleted all backup copies of windows 8.
my computer has now crashed and as a last resort i went through the reset to factory settings option which after about 2 hours stopped and gave me a black screen.
it now seems that windows 10 has been removed as well meaning i can't reset to anything.
presumably i now have to boot up from a usb with a copy of windows 8 {i believe my activation code is on the motherboard}
if this is correct how i do that?
Thank you in advance i am totally lost with this and envisage a trip to the computer shop.

 

[DSzymborski]

If you've upgraded to Windows 10, that's what you need to install (and it should be associated with your Microsoft account, so you shouldn't need a key, which you'll be unable to recover easily now). You're going to need to use another computer and use the Windows Media Creation Tool on their website to make a flash drive that can install Windows.