newbie:No reboot fix up...problem

I installed Mandriva 2006 on a "hp pavilion ze4400" everything works
fine only reboot and shutdown gives me these two in/famous error
messages:
-acpi_power_off called;
-no reboot fixup found in your hardware;
after googling I found that solutions can come from recompiling the
kernel and enabling acpi , only acpi is already enabled;
by adding acpi=off in lilo.conf but I am not sure where .I tried in
different places but no luck...;
by editing the BIOS and and set to "on" from "auto" the "start up after
power failure" line...

I have no idea what to do, any help please?
santo