You need to reinstall the os. you might learn that copying file will be an option but thats not a good option. after NTLDR, tehre are 7 other files you may need to copy. so simply and easiest way is to reisntall the os.
step 1. You can press <Alt+F10>
or the Empowering Key to launch in a Windows environment, or press <Alt+F10>
during boot up. For the Veriton desktop series, you can also press the hardware reset button
at any time. For the Aspire or AcerPower desktop series, an Acer eRecovery Management icon can be found on the desktop screen.
If this fails.
Back up all data on your computer
Insert the Windows XP disk and restart your computer.
Press any key when prompted to begin running the disk.
Press F8 to agree to the terms of service
Choose the partition you want to reinstall Windows XP on. This is usually "C:" for most users.
Choose the type of format. You can choose either "Quick" or "Full" for NTFS systems. A quick format only takes a few minutes less than the full format.
Wait for the format to complete. The Windows XP installation wizard will begin. You will be asked to choose your time zone, computer name, and to input any network information. Otherwise, the reinstall will run by itself.
The prompts during the reinstall will occur 10 to 15 minutes after the wizard begins.
Use the original product key or the Windows XP installation will not activate. You will need to call Microsoft if your product does not activate. The number is listed on the activation window.
This process will cause data loss.