Impossible to boot from cd

Hello,
I am completely lost ^ ^

I deliver my computer tomorrow, so I have the formats and I reinstalled XP.

I use a bootable cd of XP (SP3), with whom I format my PC a few months ago, and my laptop 3 weeks ago.

So I insert the CD, reboot, tap F12 to boot on the cdrom, but the pc boot XP already installed ...

I of course check in the bios, 1: Floppy 2: Cdrom 3: Hard Disk ...
I have rewritten a new cd, still the same problem ...

I did not get screen "Press any key to boot from the CD ..." I try my drive , I try each of them in slave and master.

It really must I reformat and reinstall XP I by any means.

Thank you for helping me!

Your CD readers are detected under windows and under the bios?

F12 is to enter the bios or just the Quick Menu to boot? through the bios if it is not the case ...

As can you verify that your CD is bootable on another computer?

Readers are detected under windows, but I do not see them in the BIOS ...Yes CD is booting on my laptop.

What error message do you get? What kind of CDROM drive do you have?

Finally Success !

I passed with a Clear CMOS.

Still thank you for your help.

So problem solved!