Here are boot processes of BIOS based Windows XP and Windows 7 systems. I will discuss each stage except for BIOS (POST) and Ntoskrnl.exe.** **
Boot Process (XP)
BIOS (POST) → MBR → VBR → Ntldr (Real-Mode) → Ntldr (Protected-Mode) → Ntoskrnl.exe
Boot Process (Windows 7)
BIOS (POST) → MBR → VBR → Bootmgr (Real-Mode) → Bootmgr (Protected-Mode) → Winload.exe → Ntoskrnl.exe
https://standa-note.blogspot.com/2014/