I have had this error many times.At the c:\ prompt with your XP Disk in the CDRom Drive type:

c:\copy d:\i386\\ntldr c:\
c:\copy d:\i386\ntdetect.com c:\

nb. the d:\ above is the CDRom drive letter, yours may be different, also note the space in each case before the final c:\

This may or may not help?

regards

grimerz