Mount the ISO, set your VM’s BIOS date to before May 2000, and explore carefully.
A fascinating glimpse into what could have been – essential for OS historians Windows Neptune Build 5111.iso
This build (dated December 1999) installs relatively smoothly on VMware or VirtualBox with proper IDE and legacy settings. The Activity Centers – a bold, task-based UI for home users – are the star of the show. While buggy and unfinished, they offer a clear preview of the "easy-to-use" philosophy that would later shape Windows XP’s welcome screen and task panes. Mount the ISO, set your VM’s BIOS date