recently some amount of ppl have encountered the situation that the NTLDR is missing. basically what this means is that windows can't find the bootloader in the MBR.

i'd recommend throwing your windows disk in and do a repair. the automatic repair should be able to fix the MBR without too much trouble. But i found that ppl seldomly make that disk.

Another possible repair is: go into BIOS setup and edit the boot sequence.On restart, after your computer does its POST checks, press and hold <delete> and it should take you into your systems BIOS. Go to your advanced BIOS features, and check the way your system is booting up its devices. use boot from CDrom drive for first, then floppy for second, then harddrive....etc.

you can also try the basic steps:To restore Windows XP Professional versions of Ntldr and Ntdetect.com on x86-based systems

1. Start Recovery Console by using the Windows XP Professional operating system CD.
Navigate to the system partition root and type the following commands from the Recovery Console prompt:
copy drive:\i386\ntldr

2. copy drive:\i386\ntdetect.com

In the preceding two commands, drive represents the letter of the CD-ROM that holds the Windows XP Professional installation files.

3. Answer the Overwrite system? (Yes/No/All): prompts by pressing Y.

4. Restart the computer.

However, same problem may go back to you again and again. A friend in Hall 15 encountered NTLDR missing twice. I suspect a worm. try uninstalling your virus software and reinstalling it with the latest updates. then run it. Most worms now disable your a/v on infestation is the reason to uninstall and reinstall.