ESP8266 Community Forum

last.ide.1.8.5.hardwarepath=C:\Program Files\Arduino\hardware

There is a
C:\Program Files\Arduino\hardware\arduino\avr\cores

but no
C:\Program Files\Arduino\hardware\arduino\ESP8266\cores
or something like that.
And certainly no esp.h file.

just use windows search for esp.h
it might have ended up somewhere in your user profile

I searched my entire hard disk.
No esp.h found.
There is no esp.h.

Try looking under C;\users\yourusername\appdata\

Then under either Local or Roaming see if there is a folder called something like Arduino15 and work your way down from there.