X51 R2, boots differently, lost Windows 10

When I turned on the computer, the screen I normally will see is a white Alienware logo with an Alien head next to it with TM. But this time it booted up with a line flashing instead of the Alienware logo and Alienware X51 R2 bios version A12 and loading bar. Then it booted with an Alienware wallpaper that looking like this =

But when it finishes booting, it boots to completely different version of Windows instead of Windows 10. Windows 8.1 which is the operating system that it came with and it tells me to set up up again in Windows 8.1. Purchased on June 29, 2013. Purchased warranty expired on September 30, 2014.