@luisgmarinr What you are telling me and what I see on the screen is not the same. Some of my confusion is that I don’t use virtual box so it may be something unique to VB.
You tell me the FOG server is at 10.0.2.15, but from your initial screen shot that is the IP address being given to the pxe booting computer.
The firmware is being told the next server (pxe boot server) is at 10.0.2.4. The next server field should point to the fog server IP address. Its also being told to boot win.pxe and that is not a FOG boot loader.
So lets start to debug this by identifying what device is 10.0.2.4.
Also what device is the dhcp server for your network? That device appears to be giving out bad information.