The GRUB4DOS package “grub4dos.tcz” is intended as an alternative to the GRUB package “grub-0.97-splash.tcz”.
The main use case in which GRUB4DOS supersedes GRUB is that it is possible to install GRUB4DOS in a way that it can be loaded from the Windows Boot Loader without repartitioning your drive.
GRUB4DOS is less error-prone than GRUB since its operation does not depend on a devices.map file that can be invalidated when new storage devices are added to a system. Instead of trying to remember where critical files are located on disk, GRUB4DOS searches for those files.
When GRUB4DOS boots, it searches each partition whose type it recognizes for a file /grldr in the root directory of that partition. If the loader grldr is found on some partition, then the boot loader tranfers control to grldr, which then searches for a file called menu.lst; otherwise, GRUB4DOS enters command mode.
The search for menu.lst begins on the partition where grldr was found and looks in order for /menu.lst, /boot/grub/menu.lst, and /grub/menu.lst. If none of those files is found, then all of the other partitions that GRUB4DOS recognizes are searched for /menu.lst. If menu.lst if found, then it is used to control the boot process; otherwise, GRUB4DOS enters command mode.