Worst Fears Came true today

I formatted the /dev/sda8 where Ubuntu Linux was installed.

Now after booting it is dropping to (GRUB 2 Rescue Shell)
grub rescue >
I tried ls
(hd0), (hdo,1), (hd0, 2)... is coming.

My CD Drive is not working, hence I tried to boot through the USB Installer (unetbootin-windows-442). I configured the BIOS to boot from the USB,

Now I am getting the error "Operating System Not Found". Whats the reason ??.