POSIX subsystem for Windows NT...
Anyone remember this? A bare minimum POSIX.1 subsystem included in the original NT releases - allowing MS to undercut big-iron UNIX vendors for US Gov contracts for a "POSIX compliant" OS (but not defining how POSIX it should be). Dropped shortly afterwards once they'd secured the market. Many unhappy end-users left with either a massive porting exercise, or legacy/unsupported systems.
And then there was Windows Services for UNIX (SFU) (discontinued). Not sure who that was for.
Meanwhile the first thing we do with a Windows desktop is install Cygwin and fire up bash...