To install Windows on computers with UEFI you will need an original DVD or a specially prepared bootable USB flash drive with Windows 10 for UEFI computers (or with Windows Server). Additional data partitions may be present. The main partition contains the installed Windows, programs and user data. The MSR partition must be located between the EFI partitions (ESP) and the primary Windows operating system partition. In Windows 10, the size of the MSR partition is only 16 MB (in Windows 8.1 the size of the MSR partition is 128 MB), the file system is NTFS. The MSR partition doesn’t receive a drive letter. This is a backup partition with the GUID label e3c9e316-0b5c-4db8-817d-f92df00215ae. The MSR partition (Microsoft System Reserved) on the GPT disk is used to simplify partition management and is used for service operations (for example, when converting a disk from basic to dynamic). The default size of the EFI partition is 100MB (on advanced format disks with 4KB sectors the size of the EFI partition is 260MB). The EFI partition with the FAT32 file system is a mandatory partition on GPT disks on UEFI computers and has the GUID c12a7328-f81f-11d2-ba4b-00a0c93ec93b.

Computer manufacturers or users can create their own partitions containing, for example, Windows Recovery Environment ( Windows RE) in the winre.wim file, a partition with the system image backup provided by the OEM (allows to roll back to the original state of the computer), user partitions, etc. These partitions are created by the Windows Installer when you perform a clean OS install on an unformatted drive.

Primary Windows partition (the partition containing Windows).

Microsoft Reserved partition - 128 MB (partition type - MSR).

EFI System Partition (ESP – Extensible Firmware Interface) - 100 MB (partition type - EFI).

You should have at least the following partitions:

GPT Hard Disk Partition Structure in WindowsĬonsider how the default partition table of a bootable hard drive with GUID partition table (GPT) on the UEFI computer should look like. Repair the EFI bootloader and Windows BCD.How to Manually Create EFI and MSR Partitions on GPT Drive?.GPT Hard Disk Partition Structure in Windows.

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