Windows XP Setup stops after copying files

Hello everybody!

I got a strange problem. I upgraded my W2k to XP SP1a. Everything works
fine. In control panel the computer type is "MPS multi-processor".

But with this HAL I can't take advantage of my processors hyper-threading
technology. So I tried to install the "ACPI multi-processor" HAL via Windows
Setup repair.

But after coyping installation files just before the GUI part of the setup
begins, the system stops with a blue screen: "STOP 0x0000007E, 0xC0000005,
0xF790FA59, 0xF7C8D830, 0xF7C8D530".

Could not find anything about this particular combination in the konwledge
base.

I installed a clean Windows XP on another partition. Then changed the HAL
the same way - setup works perfectly and this clean windows now runs with
ACPI multi-pro showing 2 CPUs in task manager.

What could I do to properly change the HAL on my first XP (all programs are
installed there!) and how can I prevent the STOP message (or find out what
EXACTLY causes it)???

Many, many thanx in advance.


Bye Oli