It will use the files Ntdetect.com, boot.ini, and bootsect.dos (for dual-boot machines).
It then starts the appropriate mini-file system (e.g.:FAT, NTFS), so that it can read the files from the disk.
It will then read the Boot.ini file, and display the boot menu on the screen.
If an OS other than Windows 2000 is selected, NTLDR then loads the bootsect
.dos file
and passes control to it, which then boots the other OS.