NTFS is standard
Windows 2000 will automatically use the FAT32 file system
Fat 32
Windows 2000
NTFS
Windows 2000 supports FAT16, FAT32, and NTFS partitions.
NTFS5
Windows 2000
Ntoskrnl.exe
A Windows virus scan is not performed automatically if one does not configure it to scan a Windows computer automatically. An antivirus is protecting you automatically from opening a infected file.
CDFS CD Rom File System is relatively simple format defined as the read only formatting standards for cdrom media.
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.
Windows applications in general (not just for Windows 3.1) automatically append the file extension.