I'm also searching how to get CPU's temprature via ACPI.SYS, but there is no documentation at least on MSDN. you can try to read the open source code - Linux 2.6.20 ACPI Driver .:-D
The latest version works well on vista I installed it On Dell XPS -Vista Home Premium (the bugfix version) http://www.p35-forum.de/files/nhc_2.0_pre_release_06_dell.zip[^]