If running Mac OS on a non-Apple laptop, then there’s a sting in the tail of the forthcoming 10.5.6 update: it appears that the new kernel only wants to run with ACPI HPETs, and will fail on boot if legacy i8254/RTC timers have interrupts assigned to them.
To fix this, a replacement ACPI Differentiated System Description Table is required. efi_boot, version 6.1 or above, has the ability to replace the DSDT supplied to the kernel from the system firmware with a customised one: Simply place the alternative DSDT.aml in the root of the EFI volume – generally /Volumes/EFI/.