The Boot Program Executes Ntldr, Files Needed To Successfully Boot Windows NT

4. Performed by boot sector program Processor is changed from real mode, in which all programs have full access to the entire system, to flat memory mode, in which 32-bit code can be executed.

5. Performed by Windows NT loader Minifile system drivers are started so files can be read.

6. Performed by Windows NT loader Read BOOT.INI file and build the boot loader menu described in the file.

7. Performed by Windows NT loader If user chooses Windows NT, then run NTDETECT.COM to detect hardware present; otherwise, run BOOTSECT.DOS.

8. Performed by Windows NT loader Ntldr loads information from the registry about device drivers and loads them. Also loads the HAL.DLL and NTOSKRNL.EXE.

9. Performed by Windows NT loader Ntldr passes control to NTOSKRNL.EXE; load is complete.

10. Last step performed by the loader

The Boot Program Executes Ntldr

With the execution of Ntldr, Windows NT starts its boot sequence. This program is responsible for loading Windows NT and performing several chores to complete the load.

It then passes off control to the operating system.

1. Ntldr Changes The Processor Mode And Loads A File System. Ntldr is a 32-bit program and begins by changing the CPU mode from real mode to a 32-bit mode called 32-bit flat memory mode in order to run its 32-bit code.

2. Next, a temporary, simplified file system called the minifile system is started so that Ntldr can read files from either a FAT or an NTFS file system.

3. Ntldr Reads And Loads The Boot Loader Menu. Ntldr then is able to read the BOOT.INI file, a hidden text file that contains information needed to build the boot loader menu. The menu displays and the user can make a selection or, after the preset time expires, the default selection is used.

4. Ntldr Uses NTDETECT.COM. If Ntldr is to load Windows NT as the operating system, the Ntldr runs the program NTDETECT.COM, which checks the hardware devices present and passes the information back to Ntldr. This information will later be used to update the Windows NT registry concerning the last-known good hardware profile used.

5. Ntldr Loads The Operating System And Device Drivers. Ntldr then loads NTOSKRNL.EXE, HAL.DLL, and the System hive, a portion of the Windows NT registry that includes hardware information that is now used to load the proper device drivers for the hardware present.

6. Ntldr Passes Control To NTOSKRNL.EXE. Ntldr then passes control to NTOSKRNL.EXE, and the boot sequence is complete.

7. If An Operating System Other Than Windows NT Is Chosen. If a selection was made from the boot loader menu to load an operating system other than Windows NT, such as DOS or Windows 9x, Ntldr does not complete the remaining chores to load Windows NT, but loads and passes control to the program BOOTSECT.DOS, which is responsible for loading the other operating system.

The BOOTSECT.DOS file contains information from the partition table for this particular hard drive and cannot be copied from another PC.

Files Needed To Successfully Boot Windows NT

The files needed to successfully boot Windows NT are below. (In the table, references to \winnt_root follow Microsoft documentation conventions and mean the name of the directory where Windows NT is stored, which is \Winnt by default).

File Location

Ntldr Root directory of the system partition (usually C:\)

BOOT.INI Root directory of the system partition (usually C:\)

BOOTSECT.DOS Root directory of the system partition (usually C:\)

NTDETECT.COM Root directory of the system partition (usually C:\)

NTBOOTDD.SYS* Root directory of the system partition (usually C:\)

KTOSKRNL.EXE \winnt_root\system32 directory of the boot partition

NTOSKRNL.EXE \winnt_root\system32 directory of the boot partition

HAL.DLL \winnt_root\system32 directory of the boot partition

System \winnt_root\system32\config of the boot partition

Device drivers \winnt_root\system32\drivers of the boot partition

* NTBOOTDD.SYS is only used with a SCSI boot device.