This error occurs when there is bad shutdown or the NTLDR and NTDETECT.com files get corrupted.
Boot with windows xp cd and go to recovery console. (Press 'R' to access recovery console.)
Login to the windows installation and copy the files NTLDR and NTDETECT.COM from the i386 folder to c drive.
C:\> copy x:\i386\NTLDR c:\
C:\> copy x:\i386\NTDETECT.COM c:\
Replace x with the cd drive letter.
Type 'restart' to reboot the system.
Disclaimer: Any support you choose to take here is completely at your own risk.