Microsoft has just launched Windows 10 in 190 countries. While you can get the OS via Windows Update on Windows 7 and Windows 8/8.1, Microsoft has released the official Windows 10 ISOs to make your upgrade process faster.
Keep in mind that if you will be installing the operating system for the first time, you will need your Windows product key (xxxxx-xxxxx-xxxxx-xxxxx-xxxxx).Check here
ISO