A standard Windows 8.1 installation ISO typically ranges from . To achieve a 100MB file size, developers use advanced compression tools (like KGB Archiver or high-ratio 7-Zip settings) and perform "lite" modifications:
Even if the download is only 100MB, the operating system still requires standard hardware to run effectively once uncompressed: Super Userhttps://superuser.com What are the specifications required to install Windows 8?
The core install file ( install.wim ) is replaced with a highly compressed version that expands significantly during the actual installation process.
"Updated" versions often include the latest security patches (up until Microsoft ended support) directly in the image to save the user time after installation. Minimum System Requirements
Most built-in apps, drivers, help files, and languages are removed.