Microsoft have launched a new website to allow all of you, who have not created the restoration media, to reinstall a brand new Windows on your PC.
All you need is your Windows KEY and the language of your Windows.
This will allow you to test the forecoming Windows 10 and reinstall your production Windows 7 or 8.1 safely after.
But remember, this will only perform a fresh install of Windows.
You can find this site HERE.
Sofa Tiger says : DO backup your data BEFORE.