It appears to be attempting to boot from your network
If you know how:
Enter your BIOS, and make sure that the CD/DVD drive is set to load before the hard disk drive
(Then exit and save the changes)
Or (better yet)
If (when you start the computer) your BIOS screen shows a key to load a boot menu, press that key, and select the CD drive.
This is a legal XP CD, correct?