bootmgr.exe
Windows Boot Manager (bootmgr)File,Windows boot loader (winload.exe)File and the Boot Configuration Data (BCD) File
No. Windows Vista is not based on DOS and a DOS boot disk will be unable to read the file system that Vista is on.
boot.ini
According to CompTia's A+ guide to certification in Chapter 14 pg. 52, The 2000/XP Boot Process, the three files required to start Windows XP operating system are: NTLDR, BOOT.INI, and NTDETECT.COM. If you are using a SCSI hard drive, there's a fourth file called NTBOOTDD.SYS.
Autoexec.batAutoexec.batAutoexec.bat
Nothing was techinically "replaced", but they booted in phases rather than specific files. This lead to adding bootmgr(Windows Boot Manager) which reads a registry type file that was not used in Windows XP.
Setuplog.txt
NTLDR is indeed a key boot file in Windows 2000 and all of the Windows operating systems since Windows NT. A machine will not boot without that file.
Boot Configuration Data (BCD)
boot.ini = file used to identify the default operating system and other operating systems if more than one is present. The boot.ini file has been replaced by the Boot Configuration Data (BCD) File in windows vista
boot ini
NTFS is the predominant file system although FAT is supported on XP.