problem installing ubuntu 12.04 on sony vaio with win8 and uefi

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http://askubuntu.com – I'm trying to install ubunt 12.04.3 on my sony vaio with win8 pre-installed. I want to mak a dual boot. If boot is setted in UEFI mode, I cannot load from cd. So I setted Legacy mode and I could boot from Ubuntu Live CD and install it. Everything in the setup went fine. I could allocate 100GB for Ubuntu. Eventually I had to restart after installation. Now it happens that: - If boot is in legacy mode is setted, a error message appear when I switch on the notebook. The error says "Operationg system not found". So I cannot boot neither windows8 nor ubuntu. - If boot is in UEFI mode, when I switch (HowTos)