1. BIOS (legacy systems 5-yrs+)
  2. BIOS handoff to UEFI (virtually all current systems: 1 + 4)
  3. UEFI handoff to legacy BIOS (emerging)
  4. UEFI (near future)


Hard (cold) Boot and Soft (warm) boot

In a modern IBM-PC compatible system, the difference between hard/soft boot amounts to this: soft boot bypasses the first 2 phases (see section below). More precisely: warm boot branches to the step just before phase 3. The practical effect is shorter boot time, due to skipping of power supply waiting, firmware-based hardware detection, and BIOS loaded (non-native to motherboard and the original IBM-PC architecture) storage initialization.

Boot Process of x86/x64 NT5.x

  1. Hardware Phase
  2. Firmware Phase
  3. (BIOS or UEFI+CSM, else more complicated)
  4. OS-independent boot-loader phase
  5. OS real-mode phase
  6. OS Windows phase
  7. User Logon
NT6 is boot process is similar to NT5,
except for the following file differences
NT4, NT5 NT6
bootini BCD

Most probable cause:

  1. HD/CD/DVD
  2. PSU
  3. MB
  4. Mem