Replace NTFS.sys
1. Insert your Windows XP disk and restart the computer. If prompted, press 'Enter' (or any other key) to boot from CD.
2. Type 'R' to enter the Recovery Console.

3. Type '1' and press 'Enter' to select the C:\Windows partition for repair.
4. Type 'cd \windows\system32\drivers' and press 'Enter' to navigate to the folder containing NTFS.sys.
5. Type 'ren ntfs.sys ntfs.old' and press 'Enter' to rename the existing copy of NTFS.sys. This will allow you to create a new copy of the file.
6. Type 'copy d:\i386\ntfs.sys c:\windows\system32\drivers' and press 'Enter' to copy a working version of NTFS.sys to your Windows system folder.
7. Type 'quit' to exit the recovery console.
8. Restart the computer.
Run Microsoft's CHKDSK Utility
9. Insert your Windows installation disk and restart the computer. If prompted, press 'Enter' (or any other key) to boot from CD.
10. Type 'R' to enter the Recovery Console.
11. Type '1' and press 'Enter' to select the C:\Windows partition for repair.
12. Type 'chkdsk /r' and press 'Enter.' Type 'Y' if prompted to unmount the volume.
13. Type 'exit' when CHKDSK has completed and restart the computer.
Perform a Repair Install
14. Insert the Windows XP installation CD and restart the computer. Press 'Enter' (or any other key) if prompted to boot from CD.
15. Press 'Enter' to install Windows.
16. Select your Windows installation (usually C:\Windows) and press 'R' to begin a repair install. A repair installation replaces your Windows system folder with a fresh copy, but it leaves your accounts and files intact.