Another thing I should note, is changing the HAL is only possible,
if the PC is compatible with the HAL you are trying to use.
The PC I had, where I ended up with "Standard PC", there was
a reason for that to happen. The BIOS on the computer (on an Asus
motherboard), just happened to have a defect in the support for
ACPI. When the Windows installer disc was used, I wasn't paying
close attention. There was a warning that "this BIOS is not
compatible with ACPI" or words to that effect. The installer
then installed "Standard PC" as its response to the bad BIOS
design. If the BIOS doesn't properly support ACPI (ACPI tables
should be passed from the BIOS to the OS), then the installer
is not going to be able to install an ACPI HAL.
To install the "ACPI" kind of HAL, I actually had to flash upgrade
the BIOS to the next available version. The ACPI problem in the
BIOS was fixed.
If you try and force a HAL, when the problem is with the motherboard
and the BIOS, then obviously the OS will be "very unhappy". As in
busted and potentially non-bootable.
You should do more research, regarding the make and model of computer,
the motherboard and BIOS version, to see if this is a known problem.
Also, check the BIOS settings themselves. Sometimes there are
settings in the BIOS, that affect ACPI. In particular, some BIOS
offer an option to support ACPI version 2.0. Sometimes, only one
of the ACPI options seems to be working. So do a little checking
first, before trying to change the HAL. Using whatever means
anyone else may contribute to this thread.
Fixing the BIOS, does not immediately cause the OS to change
the HAL in response. When you fix a BIOS, so that it supports
ACPI properly, that enables you to attempt a change of the HAL
at the OS level. But the OS doesn't immediately go "oh, I see
an ACPI motherboard" and fix it for you. The fix must be
initiated by the user.
If the CMOS battery on the motherboard has gone flat, and
some of the BIOS settings were forgotten or reset, that is
a possible reason for something important in the BIOS, to
have a changed value. So have a look around first.
Paul