New build - Can't boot from a dvd-rw

Hi,

I've just finished assembling my brand new build and it seems that I can't boot from a dvd-rw.

My mobo is a Gigabyte GA-P35-DS3L and my dvd drive a Pioneer 212D Sata.

If I insert my WinXP CD, it is dectected and boots from it.
If I insert a dvd-rw with Ultimate Windows Boots disc on it, it doesn't boot from the dvd drive just like if I had inserted a non bootable disc.

I played a bit with the bios settings and I found that if I enable the AHCI thing I can finally boot from the dvd-rw. But I read that enabling that option can cause some troubles.

On my old rig, the dvd-rw boots fine with a Plextor P716a.

I need help on this, I'm not familiar with SATA dvd drive.

thanks for your help.