I've got gentoo installed and running after some battles with the nvidia drivers.
Anyhow, it's not 100% of course, and I'm sort of disappointed with it. I have a catch 22 - I need ACPI so that linux will shutdown and turn off my pc, but I can't have ACPI and X (nvidia?) running - ie, starting X with ACPI in the kernel causes the system to freeze with ascii characters, and only ctl+alt+del will let me reboot.

Also, I'm unable to boot into WindowsXP if I disable ACPI in the BIOS. So Things are a bit sucky. I have ACPI enabled i nthe BIOS which is fine, I don't have ACPI in the kernel - which is what I want, and I have X with nvidia drivers working.

So I'm left with a PC that won't shutdown from Linux.

Perhaps someone has some experience, ideas etc?
I have tried the APM modules, they didn't do anything for me. I've tried multiple kernel sources and get the same thing.

You mention you tried the apm modules - did you load the apm daemon (apmd) after you loaded the modules?

If you're getting errors stating that you can't load apm because you already have ACPI enabled then you'll need to stop ACPI first.

I put apm in the modules.autoload file, and startup indicated that the apm module was loaded ok. However, I don't know anything about apmd!!!
Oh, I can shutdown now -h and the machine will run the shutdown procedure correctly, with the last thing you see (and it stays there ) is 'Powerdown'.
So when you get to that point, you actually have to turn off the machine.
Just wanted to make that clear

Try opening a console and type in (as root) apmd to load the apm daemon. Now 'halt' your machine and see if it turns off properly. If not have a look at the BIOS and see if you can enable both ACPI and APM (most machines are capable of this).

Last night when I came home, I run apmd to start the daemon. Then I did shutdown now -h (is that the same as 'halt') but the same thing, it just runs the shutdown script, then stops at 'Powerdown'. I have to have ACPI enabled in the BIOS, otherwise WindowsXP won't boot (and I have to keep it around to play some games on, and unless I work out how to get winex to run them). I haven't noticed in the BIOS apm options anywhere, and I've been in there a LOT!
When the machine does the 'Powerdown' I do hear a click in the machine as if it is trying to turn it off, but it doesn't actually do it. Does this tell you anything?