I just switched my PC's case from an AT to an ATX one. I have Mandrake 10.0 OE (stock kernel 2.6.3-7mdk) and Mandrake Cooker (custom 2.6.8.1-10mdk). None of them can power-down properly.

My Mandrake 10 prints out a crash page when it tries to power down while the cooker simply says "power down" and lets me push that little button. The kernels both have APM and ACPI compiled, but I don't know what can be the problem. Windows XP powers down cleanly.

I pass at boot the acpi=ht option to the kernel. Can this be the problem? Can I try using APM instead of ACPi or vice-versa? If yes, how?

Well, it seems I was right.. the acpi=ht was the little bugger. It now powers down as expected

I guess it all depends on your hardware whether "acpi=ht" can cause shutdown problems. I have "acpi=ht" enabled on cooker (box 1) and on mdk 10.0 (box 2) [see sig] and "acpi=off" on mdk 9.1/9.2 (box 2) and never had problems with shutting down.

BTW, you list kernel 2.6.9 in your distro list. Is that vanilla? And how's it running?