Despite its compact size, the highly compressed Windows 8.1 still packs many of the features you're familiar with:
Searching for a "600MB highly compressed" version of usually points to unofficial, modified ISO files created by third-party enthusiasts. These versions (often called "Super Lite" or "Extreme Compressed") remove a massive amount of system features to achieve such a small file size. Key Features of a 600MB Version Windows 8.1 Highly Compressed 600mb