In XP and earlier, it's called boot.ini. In Vista and 7 (and possibly future OSes), you have to use a program called bcdedit to change the bootloader.
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To change the contents of the boot loader menu in Windows XP, one must edit the boot.ini file.
Bootsect.dos
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The boot loader performs POST.The boot loader is loaded from RAM.The boot loader initializes the flash file system that is used to boot the system
Windows Boot Manager (bootmgr)File,Windows boot loader (winload.exe)File and the Boot Configuration Data (BCD) File
The Ntldr file reads and loads the boot menu in Windows XP. The file runs from the hard drive but can be run from portable storage devices.
/boot directory is where all the file to boot Linux are stored it include the kernel image , initial ram disk. This files are read by the boot loader at the boot time.
BOOT.INI: A text file that contains the boot loader menu that is displayed on the startup screen. BOOT SECT.DOS: Responsible for loading the operating system other than the default operating system. NTOSKRNL.EXE: A kernel file that contains the windows xp core and loads the operating system device drivers. HAL.DLL: Hardware abstraction layer (HAL) driver that holds information specific to the CPU that the OS is running on. SMSS.EXE: A file that contains information to carry out pre -start functions such as running in boot - time version of CHKDSK called AUTOCHTC.
By "boot label", I presume you mean it's name as it appears in the boot menu. You can change this by editing the boot menu in question.For GRUB:The GRUB menu can be found in /boot/grub/menu.listFor LILO:The LILO menu can be found in either /boot/lilo/lilo.conf or /etc/lilo.confFor SYSLINUX:The SYSLINUX menu can be found in either /boot/syslinux/syslinux.cfg /syslinux/syslinux.cfg /boot/syslinux.cfg or in the root directory.For NTLDR (the Windows bootloader):The NTLDR menu can be found in the boot.ini file of your C:\ drive
For older versions it is "/etc/lilo.conf" and for newer versions "/boot/grub/grub.cfg".
C:\Windows\Ntbtlog.txt