I don't have that option in my BIOS. It's from 2000, that may be why.
I disconnected the mouse and rebooted -- no help. Must be some other change I made around the same time, but I haven't been able to nail it down yet.
What's happening more specifically is that using "halt" or shutting down from kdm or kde will power the computer down properly, and turn it off. Pressing the power button does absolutely nothing. I see the socket open for acpid from "netstat -l" and /var/log/acpid shows it's reading "/etc/acpi/events/default" which is just how I've always had it set up. acpi is in memory. Since the BIOS is from 2000, I have to pass the option acpi=force to lilo, which is something that's been working ever since I set it up.
I have upgraded some packages recently, but can't find any in /var/log/removed_packages that could possibly relate to acpi. I'm using Slackware 10.2, updating from slackware-current. I think the next thing I'll try is just installing the 2.6.x kernel series. I have been using the 2.4.x (bareacpi). I don't know what else to try at this point. I do like being able to use that power button though.