Install Windows 7 Ultimate x64 as UEFI with GPT

gptinstallationuefiwindows 7

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.

Best Answer

"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.

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Installing Win 7 To GPT and Why My UEFI Mobo Won’t Boot From CD Unless In Legacy Mode

My first suggestion is to upgrade your firmware. Check your manufacturer's Web site for such an upgrade. (It will probably be called a "BIOS update" or something similar; manufacturers usually call their EFIs "BIOSes," although IMHO this just creates confusion in the long run.)

My second suggestion is more of a comment: The Windows 7 disc is a bit weird when it comes to EFI-mode booting. There are various Web pages that describe this and provide workarounds, but the only one I have bookmarked is my own page on DUET. The section "Installing Windows Under DUET" describes the procedure, but it's somewhat DUET-specific. A Web search might turn up something that's more directly applicable to your situation. Of course, if you're having problems with other EFI-mode boot discs, too, the Windows 7 issues obviously won't apply to them.

If these suggestions don't help, I recommend you try using my rEFInd boot manager to detect your CD/DVD as an EFI-bootable device. You can theoretically do this without mucking with your hard disk by using rEFInd on a USB flash drive, but if your firmware is flaky about booting external devices in EFI mode, you might need to install rEFInd on the hard disk. If you install rEFInd on the hard disk and it doesn't work, you might try installing the ISO-9660 driver that comes with rEFInd. The ISO-9660 driver probably won't help with the Windows 7 disc, but it might help with some others.

Windows – Install Windows 7 on mbr hard disk with UEFi firmware

From UEFI Wikipedia page:

To ensure backward compatibility, most UEFI firmware implementations on PC-class machines also support booting in legacy BIOS mode from MBR-partitioned disks, through the Compatibility Support Module (CSM) that provides legacy BIOS compatibility. In this scenario, booting is performed in the same way as on legacy BIOS-based systems, by ignoring the partition table and relying on the content of a boot sector.

BIOS-style booting from MBR-partitioned disks is commonly called BIOS-MBR, regardless of it being performed on UEFI or legacy BIOS-based systems.

Furthermore, booting legacy BIOS-based systems from GPT disks is also possible, and such a boot scheme is commonly called BIOS-GPT.

Windows installation booted from EFI, does not allow installation on MBR disks and vice versa.
EFI installation needs EFI partition scheme TO BOOT (correct me if I'm wrong)

like:

Partition   FileSystem   Size   Purpose

EFI         FAT32        100MB  EFI Boot Sector on GPT disk
MSR         N/A          128MB  Hidden Services Partition for GPT disk
Primary     NTFS         N/A    Windows Installation/Data Volume contaning VHD

But, it can load windows from another MBR disk (or VHD) in CSM mode. So, to accomplish this, you need at least 2 disks, or 1 physical GPT disk, containing a Virtual MBR disk.

Best Answer

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