Windows 2003 Boot Process:

1. POST
2. The MBR reads the boot sector which is the first sector of the active partition.
3. Ntldr looks path of OS from boot.ini
4. Ntldr to run ntdedetect.com to get information about installed hardware.
5. Ntldr reads the REGISTRY files then select a hardware profile, control set and loads device drivers.
6. After that Ntoskrnl.exe takes over and starts winlogon.exe which starts lsass.exe

Windows Server 2008 Boot process.

1. System is powered on
2. The CMOS loads the BIOS and then runs POST
3. Looks for the MBR on the bootable device
4. Through the MBR the boot sector is located and the BOOTMGR is loaded
5. BOOTMGR looks for active partition
6. BOOTMGR reads the BCD file from the boot directory on the active partition
7. The BCD (boot configuration database) contains various configuration parameters( this information was previously stored in the boot.ini)
8. BOOTMGR transfer control to the Windows Loader (winload.exe) or winresume.exe in case the system was hibernated.
9. Winloader loads drivers that are set to start at boot and then TRANSFERS the control to the windows kernel.

Windows 2003 Boot Process:

Windows Server 2008 Boot process.