Xp will not boot

Hello,


the problem i have is i want to repair xp but the windows cd will not boot to the install screen'
the system keeps booting off the hard drive and not recognizing the cd in the drive

i had this problem on original install but can't remember what i did to fixx the problem.

Asus p5gd1-vm
sata wd80 gig
asus dvd rom ide
winxp sp2

this also happened to me with the same setup on an Asus p5ld2-vm

any help would be greatly appreciated,

thanks pipco