“NTLDR is missing” problem in Windows XP.

NTLDR is the boot loader for Windows NT operating systems including
Windows XP.It runs from primary hard drive to load the OS selected from
the startup menu with the help of boot sector in a file.

Components important to load OS:
NTLDR: contains boot loader
boot.ini : system file which stores list of Operating Systems
to be shown at start up .
ntdetect.com: detects basic hardware required to start the operating system.
ntoskrnl.exe/ntkrnlpa.exe : stores kernal image of Windows NT systems &
responsible for various system services such as hardware virtualisation process and memory management, etc.

Here’s how u can get back into your Windows XP.
1. Insert the Windows XP bootable CD into the computer.
2. When prompted to press any key to boot from the CD, press any key.
3. Once in the Windows XP setup menu press the “R” key to repair Windows.
4. Log into your Windows installation by pressing the “1″ key and pressing enter.
5. You will then be prompted for your administrator password, enter that password(Usually it is
password,if not set)
6. Copy the below two files to the root directory of the primary hard disk.
The CD-ROM drive letter may be different on your computer.
Here it is “e.”

copy e:\i386\ntldr c:\
copy e:\i386\ntdetect.com c:\

7. Once both of these files have been successfully copied, remove the CD from the computer and reboot.