Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Windows NT startup process is the process by which Microsoft''s Windows NT, Windows 2000, Windows XP and Windows Server 2003 operating systems initialize. In Windows Vista and later, this process has changed slightly. An NTLDR file, located in the root folder of the boot disk, is composed of two parts. The first is the StartUp module and immediately followed by the OS loader, both stored within that file. When NTLDR is loaded into memory and control is first passed to StartUp module, the CPU is operating in real mode.