Microsoft released an official "Thin PC" for enterprise VDI environments. It’s based on Windows 7 SP1, requires only 1GB RAM and 16GB storage, and is fully legit. You can still find legal evaluation copies.
Here is an interesting breakdown of what makes these builds special—and why they are a bit of a "living on the edge" experience. 💿 The "Magic" of the 700 MB ISO These unofficial builds, often created by enthusiasts like Khatmau_sr Windows 7 Ultimate Lite Edition 700 Mb Only Iso