Choose "Custom: Install Windows only (advanced)" if you want a clean installation. This allows you to delete old partitions and start fresh.
Follow these steps to get the official ISO file from the Microsoft website : download windows 8.1 disc image -iso file- - microsoft
Follow the on-screen instructions. Select your language, time, and keyboard preferences. Choose "Custom: Install Windows only (advanced)" if you
Windows will copy files and restart several times. Follow the prompts to set up your user account and preferences. Important Safety Note download windows 8.1 disc image -iso file- - microsoft
You will see two options: 32-bit Download or 64-bit Download . Choose 64-bit if your computer has 4 GB of RAM or more. Choose 32-bit for older systems with less RAM.
You can find troubleshooting steps and community support on the Microsoft Community Hub or Microsoft Q&A .