Fedora 7 has acpi enabled by default. A quick check: chkconfig --list | grep acpi
acpid 0:off 1:off 2:off 3:on 4:on 5:on 6:off
But as a suggestion boot with a live Linux CD or into rescue mode from the installation media and check the root partition for the hidden file .poweroff, if not present then remove the hidden .shutdown file and create the .poweroff file using the touch command. The root partition has to be mounted read/write for this.