Windows Booting Simplified
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This article is not intended to be a detailed accounting of how Windows boots in the 'modern world' (which is essentially Vista and above). The 'old fashion' Windows NT 4, 2003 boot methods are not addressed here. See the last section for some links on more detailed information.

Modern PC Booting for Windows based on x86, i386, x64, whatever you want to broadly label the Intel 8086/8088 - IBM PC lineage

  • Power is turned on
  • CPU starts a program ("First Boot Program")
  • Hardware is / can be tested by the "First Boot Program" (if issues, booting is halted / can be halted)
  • "First Boot Program" starts a "Second Boot Program" (Bootloader)
  • "Second Boot Program" loads other programs and starts Operating System (Windows, Linux, etc.)
  • Operating System boot completes, computer is useful (hopefully)

This is a really simplified perspective on booting,

MBR (Master Boot Record) VS UEFI (Unified Extensible Firmware Interface, sometimes referred to as just EFI)

Again, this is not a detailed explanation...

Windows can boot (the "Second Boot Program" as referred to above) via two methods.

  • Computer is powered on and begins boot process.
  • "Second Boot Program"

Odd Microsoft Quirk (go figure)

No, all the documentation you read is not messed up. Microsoft refers to the Partition / Volume that contains the "Second Boot Program" as the "System Partition / Volume". The "Boot Partition / Volume" is where Windows Operating System files are located. The Boot and System Partition can be on the same Partition / Volume. It helps if you think about this from a vain, myopic, selfish "Microsoft Windows" perspective where the 'real booting' only begins with Microsoft Windows.

Top Tips

  • BCD Editing Software: EasyBCD, BootIce (older program that may have some issues with latest version as some websites claim, but haven't personally experienced)
  • MBR and UEFI (EFI): Even if there's only one OS / Volume / Partition bootable, it is a good practice to make sure the /Boot/BCD ("MBR Booting") File and /EFI/Microsoft/Boot/BCD ("UEFI / EFI Booting") File have duplicate boot information, just in case something gets changed in the BIOS.
  • Windows 11: Almost everything you might have heard about Windows 11 booting is not accurate. Windows 11 is fully functional and can boot VIA "MBR Booting" (as opposed to "UEFI / EFI Booting") on an "MBR Partition / Volume" (as opposed to a "GPT Partition / Volume") without any TPM (Trusted Platform Management, as in MANAGEMENT by Microsoft (and other software vendors) of your PLATFORM, NOT YOUR management of YOUR platform, regardless of what Microsoft claims it is "good for") support.
  • Metro Loader: Avoid it. Looks cool, but starts at a later point in the boot process than the "Text Loader" which makes it less useful if there are any boot issues that need to be diagnosed.
  • FixMBR and FixBoot, for more control, use BOOTSECT instead of BOOTREC (Example: BOOTSECT /nt60 v: where /nt60 = an MBR Boot Record for Vista and above, v: = The drive letter assigned to the partition (may need to be assigned with DISKPART)
  • BCDBOOT Command can add necessary files to change a non-system partition to a system partition. (Example BCDBOOT C:\Windows /l en-us /s X: /f ALL /v with C:\Windows = Source of Files to be Copied, /l (that's a lower case L, not a capital I / 'eye') = "local language", /s = Drive Letter to copy files to (may need to be assigned with DISKPART if no drive letter has been assigned to parition), /f = ALL is UEFI and MBR Boot Files (as opposed to just MBR or UEFI), /v = Verbose)
  • DISKPART can be used to assign a drive letter for using the BOOTSECT and BCDBOOT commands (Example: DISKPART, SELECT DISK, SELECT VOL, ASSIGN LETTER=WhatEverUnusedDriveLetterDesired)
  • MSCONFIG, Boot Tab: A "neutered" version of BCDEDIT, EasyBCD, BootICE.

System Partition Designation

When looking at all the Disks and Partitions / Volumes in Disk Management, the "System" (as in System Partition) is not a value that can be assigned, unlike "Active" (as in Active Partition) which can be set. The System Partition Designation is actually determined, rather than set. IE, if a computer is booted up from Disk X, with an MBR on Disk X, with BCD Information on Disk X that indicates the Windows OS is on Disk Y, then Disk X will be have the System Partition Designation assigned to it.

Links for more Detailed Information


MBR Booting (and repair):