The NTLDR is a basic part of the boot process in Windows 2000 and XP. It does not often get "lost", but this error message could mean the disk has been damaged or removed or the wrong drive was selected in the BIOS. This happens also when you leave a floppy in the drive.
First thing is to check the BIOS settings and see if the right boot order is selected. If the C MOS battery is dead, the BIOS may have reset itself to bad settings. You can verify the presences of the Hard Drive and the CD ROM drive within the BIOS. The CD-ROM should be the first boot device. That is needed to do diagnostics with the original XP or 2000 install disk.
In the recovery console you can use the command 'fixboot' to restore the NTLDR. B but this is to no avail if the wrong drive was selected by the BIOS.
Hope this is of some help.