I am running windows eight alongside Ubuntu 12.04 , using the default GNU Grub (Ubuntu loads first then i used to choose Windows 8 from the list).
The computer was running normally, until just now, I booted it up and tried starting windows eight. It gives the following error:
operating system not found, try disconnecting disks that may contain an OS.
Note that I was not trying to install/uninstall/repair anything, I just tried to start Windows 8 from grub and it gave the error.