Why is it showing error of NTLDR missing?

Why is it showing error of NTLDR missing?

It's because your computer is trying to boot from a non bootable source, or your hard disc drive BIOS properties are not set like they need to be.

Here is how you can fix that.

After you check (in BIOS) that your 1st boot device is really hard drive, and if this don't resolve your problem, you could put cd/dvd rom as 1st boot device and insert the Win XP cd in your computer and when asked to press any key, press any key to boot from CD.
When you enter the setup menu you should press key "R" for repairing of Windows.
You need to log into Win installation by pressing number 1 on your keyboard and pressing enter after that.
After you enter you admin password you need to copy below lines of code in the root directory of primary hard disc.

copy d:i386ntldr c:
copy d:i386ntdetect.com c:

You must be careful, in this example d stands for CD-ROM drive letter, but in your case it doesn't have to be d, it can be some other letter, you just need to see which letter stands for CD-ROM drive on your computer.

When you do that you can remove CD from computer and reboot the computer.