How to first boot cd rom of presario 2100

Hi i have the same problem, trying to install xp on a presario CQ70 there is now ubuntu on it(but the girlie does not really like is :)

so i set cdrom to first boot.... reboot... hit the f9 for bootoptions.. and then the cdrom... well it just boots ubuntu after that, seems like it is secured for cdromboot 🙁

kind regards
 

so tht i can install an os of window 7