I bought a Samsung laptop (Model: NP350V5C-S0BIN) which came preinstalled with Windows 8. I dont like Windows 8 and want to install Windows 7. I have disabled FAST BOOT and SECURE BOOT.

My questions are.

1) On disabling Secure Boot, I found three OS Selection Modes namely, "UEFI", "CSM OS" and "UEFI or Legacy OS". Which one should I choose to install Windows 7 x64 and Why? (Really confused as in some forum they are telling to use UEFI while few other forus telling "UEFI or Legacy OS")

2) I converted the GPT to MBR once I tried to install windows 7 unknowingly but the installation failed. So if I select UEFI DVD Drive to install, will it automatically convert MBR back to GPT upon creating partitions?

Please provide the sufficient help.

  • " some forum " it might help us if you linked that forum here so we know what you are talking about. Quote literally in case the post ever disappears. – user 99572 is fine Sep 1 '13 at 12:57

"CSM" and "legacy" are synonymous in this context, so -10 points for clarity to whoever wrote your firmware's user interface. Since you want to install in EFI mode, the "UEFI" option makes the most sense; if the names are truly descriptive of their effects, this will force the computer to boot in EFI mode, which is what you want. The "UEFI or Legacy OS" option might also work, but is more hit-or-miss -- there's really no way to know in which mode the Windows installer will boot. If it boots in EFI/UEFI mode, then the effect will be identical to using the "UEFI" option; but if it boots in BIOS/CSM/legacy mode, you'll be wasting your time. You should definitely avoid the "Legacy" option. A caveat: Many firmware interface options are very poorly named, so you may find that these options don't have the effects that they seem to describe.

I don't know offhand what the Windows installer does when confronted with an MBR disk during an EFI-mode installation. It might work fine, particularly if the disk has no partitions; but if you want to be 100% certain that you're installing in EFI mode, you might want to pre-partition the disk using GPT. Personally, I'd use a Linux live CD for this, like Parted Magic or System Rescue CD; but if you're not comfortable with Linux, you may prefer to use a Windows emergency disc and Windows tools. Either way, ensure that the disk uses GPT and the Windows installer can take care of the rest.

  • The windows installer complains that "Windows cannot be installed on this disk. It is of type MBR". or something to that effect. – Milind R Nov 6 '13 at 16:15

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