driver ATI Mobility Radeon 2400 crashes windows XP

Hi! I just buy an Acer TM7720 with 2Ghz Intel Centrino Core2 duo, chipset Intel GM965 and ATI Mobility™ Radeon® HD 2400-XT graphics card.

I've deleted preinstalled windows vista home edition, and installed windows XP Pro 32 bits Service Pack 2, with the drivers downloaded form acer.com & intel.com.

When I start connected with AC adaptator, all works fine, but, when I start with battery power, system crashes, the screen freenzes in different moments of startup and nothing responds, mouse, Alt+Crtl+Del, etc. Only a few seconds pressing power button can power off my acer.

First, I think there are a battery problem, but if I uninstall ATI driver, all works fine with battery power, or if I start with F8 Press key and select "fail safe?" (a prueba de fallos) option, works fine too...

I am lookin for updated ATI driver, but in ATI download & support can't find "ATI Mobility™ Radeon® HD 2400-XT" driver, other drivers like "2400 (no mobility)" or "mobility (not 2400)" tells me no hardware compatible found.

I think there is an issue with power save strategy (windows or chipset) and ATI drivers, what can I do?

Thanks. I'm sorry my ugly english