Ubuntu / Windows: to boot one or other I have to manually change os mode selection

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http://askubuntu.com – On a new Samsung laptop with Windows 8 pre-installed I installed Ubuntu. I'm not an expert at all, I've just followed various instruction available in the web. Now, if the OS manual selection is on CSM OS it will boot Ubuntu, giving me the option of booting Windows (loader). but if I press that, it will tell me that the boot is corrupted and I can't go on. If I re-boot and select Ubuntu it boots it normally. Now, if on the other hand the OS MANUAL SELECTION IS ON "UEFI" OR "UEFI AND CSM OS", it will start Windows 8 automatically. So, basically, I have to manually change it every time I want to (HowTos)