I have a Sony Vaio SVE14A27CXH that came with Windows 8 and UEFI BIOS from factory. I have been trying to install Ubuntu 13.01 with no success. I have already suffered with "Operating System not found" because I haven't turned off safe boot. But now I am using UEFI without Safe Boot. This is the only way I don't get that message when I try to turn on my computer. But it always goes directly to Windows 8. After the Vaio screen, Grub does not show up, so I have no way of accessing Ubuntu other than my Live USB drive. Maybe I misunderstood the instructions to install Ubuntu in a computer with UEFI BIOS, but this current configuration is the only one where I can still use Windows at least. Thanks in advance.
In Ubuntu Live from the USB stick, use a program called "Boot Repair". It'll fix the GRUB for you. But I don't know what will happen with Win8 :P Its supposed to fix it! If you dont have it on the USB, install it.