If WinXP will not start, it may be due to a damaged boot sector or a missing or corrupt ntldr or ntdetect.com files. To replace, access the recovery console and enter:
1. Copy X:\i386\NTLDR C: (X is your CD ROM drive letter)
2. Copy X:\i386\NTDETECT.COM C:
Also, you may try "fixmbr", "fixboot" and then run "bootcfg /rebuild"