NTLDR

NTLDR was the program that loaded Windows NT based operating systems until Windows Vista where it was replaced with BOOTMGR. It is run from the C: drive but can also run off of a USB flash drive or DVD-ROM. It can also load non Windows based operating systems such as Ubuntu.

NTLDR needs two files on the C: drive so it can work:

 , the program that does the actual loading
 , needed for loading NT-based operating systems

Another important file is a the boot.ini which contains the settings for booting.

 References 

Category:Windows (architecture)