NTLDR's first action is to read the file. It allows the user to choose which operating system to boot from at the menu. For NT and NT-based operating systems, it also allows the user to pass preconfigured options to the kernel. The menu options are stored in , which itself is located in the root of the same disk as NTLDR. Though NTLDR can boot DOS and non-NT versions of Windows, cannot configure their boot options. For NT-based OSs, the location of the operating system is written as an ARC path.
bootsect.dos is the boot sector loaded by NTLDR to load DOS, or if there is no file specified when loading a non NT-based OS. is protected from user configuration by having the following
file attributes: system, hidden, read-only. To manually edit it, the
user would first have to remove these attributes. A more secure fashion to edit the file is to use the
bootcfg command from a console.
bootcfg will also relock the file (setting the file back to system, hidden, and read-only). Additionally, the file can be edited within Windows using a text editor if the folder view option "Show hidden files and folders" is selected, the folder view option "Hide protected operating system files" is unchecked, and the "Read-only" option is unchecked under the file's properties. Extreme caution should be taken when modifying , as erroneous information can result in an OS that fails to boot.
Example An example of a file, extracted from a working Windows XP Professional installation: [boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS [operating systems] multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect Note: If the boot loader timeout option in is set to 0, the NTLDR boot menu does not appear. This happens especially on multi-booted systems; the boot menu also does not appear when only one option is defined in (or if only one operating system is installed), like the example above, even if the timeout option is set into any other value other than 0.
NT kernel switches Note: Unless otherwise stated, the following kernel switches apply to both Windows XP and Windows Server 2003 as well as prior versions of Windows NT. • '''''' Option used only on 32-bit
x86-based systems that allocates 3 GB for the user-mode address space and 1 GB for the system-mode (or kernel-mode) address space (more than that of the 2 GB allocation used for both user-mode and system/kernel-mode address spaces). It is intended for programs that can take advantage of the additional memory address space, such as certain Windows Server 2003 and
Microsoft Exchange Server 2003 configurations. Activating this option however may break VMR-9 video; it may also cause audio problems with certain
Sound Blaster X-Fi sound cards (X-Fi Gamer / X-Fi Titanium @ WINXP 32-bit 3/2012) due to the way that
Creative's drivers handle memory over 2 GB. • '''''' Starts Windows in "
VGA mode", where a VGA-compatible
display driver is used with a 16-color, resolution. •
Safe Mode with Networking () Default mode together with the drivers necessary to load networking. • '''''' Option used only on 32-bit x86-based systems that allows applications to be given a larger address space specified by the user, similar to the switch. The aforementioned switch is mandatory when using the switch. • '''''' Allows booting of non-NT versions of Windows (e.g.
Windows 9x) using . • '''''' Allows booting of DOS or non-NT versions of Windows (e.g. Windows 9x) using . • '''''' Overrides the year set by the computer's clock settings (e.g. sets the year to 2000 within Windows, even if the year is set to 1999 within the computer's clock settings). Was used for testing
Y2K compliance. == See also ==