When I first started the switch from APM to ACPI I didn't realize the kernel needed to be patched. My problem (insanely loud fan) was fixed just by upgrading to 2.4.20 (Debian packaged kernel with an earlier patch from acpi.sourceforge.net). Unfortunately after the first upgrade I wasn't able to halt my computer without using the power switch to power-down my computer. It wasn't until later that I realized I had an old, ineffectual ACPI patch. This HOWTO was written to summarize the install process for myself, and hopefully help others who are also having a hard time finding information about ACPI. Please note: the main article outlines The Debian Way of doing things. There is also generic information in the Appendix B for those of you who prefer ... the generic way.