Upgrade to hyperthreading CPU

KB article 810231 says that after enabling hyperthreading
in the BIOS setup, Windows XP automatically upgrades the
hardware abstraction layer to support it. Unfortunately,
my Windows XP Pro (OEM CD including SP1a) does not do
that; it shows two CPUs in Device Manager, but only one in
Task Manager or programs like WCPUID. I found a web page
describing a method to do it manually. It involved only
two files, hal.dll and ntoskrnl.exe, which had to be
replaced with the multiprocessing versions from the
Windows CD. After I did that, new hardware was found, and
hyperthreading seems to work. I then re-installed update
811493 to upgrade ntoskrnl.exe. My question: Are there
other files that have to be updated, or is that really the
whole deal?

Christian Schmadalla