If you get an error that NTLDR is not found during bootup,

1. Insert and boot from your WindowsXP CD.

2. At the first R=Repair option, press the R key
Press the number that corresponds to the correct location for the installation of Windows you want to repair.
Typically this will be #1

3. Enter in the administrator password when requested

4. Enter in the following commands (X: is replaced by the actual drive letter that is assigned to the CD ROM drive.
COPY X:\i386\NTLDR C\:
COPY X:\i386\NTDETECT.COM C:\

5. Take out the CD ROM and type exit