Windows 10 Version 1507 (Threshold 1) was the original launch version of Windows 10, released in July 2015. A "Lite" version of this specific build is typically a third-party modification designed to strip away telemetry, bloatware, and heavy background services to improve performance on older hardware. Why Version 1507?
You have an old Core 2 Duo PC with 2GB of RAM. You want to emulate NES/SNES/PS1 or play 2005-era PC games (Half-Life 2, GTA San Andreas). 1507 Lite gives you near-Windows XP performance with better stability and modern file system support (exFAT for large ROMs). windows 10 1507 lite
The Original Start Menu: A blend of the classic list and modern live tiles that is less cluttered than current versions. Action Center: The first iteration of the notification hub. Windows 10 Version 1507 (Threshold 1) was the
en_windows_10_multiple_editions_version_1507_x64_dvd_6846435.iso (Get from Microsoft's old download center via archived links).