I just replaced my Hercules (=Guillemot) Firewire Video-Editing Card
DV Action Pro with a model from the same manufacturer called
VideoAction.
Suddenly, Windows XP does not boot anymore, even in safe mode. It
seems to load drivers, but then crashes with a bluescreen, saying, the
BIOS ist not ACPI-compatible, in order to prevent problems, windows is
shut down.

I safed my XP installation in an image and tried to install a fresh
Windows XP. In the initial process, XP gives out the warning, that the
motherboard is not fully ACPI compatible and therefore, ACPI must be
disabled - then refuses the XP installation. Of course, I can shut off
ACPI in the BIOS, but that was not the case before I installed the new
card - ACPI worked fully and without problems.
Here is my system: 
MoBo MSI K7T266 Pro2Ru (latest BIOS, AMI ver. 3.7,
http://www.msi-computer.de/produkte/produkt.php?Prod_id=175&Seite=BIOS),
Promise IDE COntroller 100 TX2 (Pci-Slot 1), 
GRaphics Card ASUS 7700 Deluxe, 
SoundCard Soundblaster Live! (PCI-Slot 2), 
Realtek LAN (PCI Slot 3), 
( VideoACtion Slot 4 - eventually replaced again by the DV Action Pro) ,
 DIgital Recording Card RME DIGI 96/8 (Slot 5). 
Athlon 2000+, 768 MB RAM.

The following steps I have already taken:
1.) Loaded my already working system again from the image I have stored.
Assigning an IRQ to the VideoEditing Card VIDEO ACION in the BIOS.
Still getting bluescreens.
2.) Switching the VideoAction to another PIC-Slot (tried 2 and 3),
assigning it an IRQ in the BIOS - same problems
3.) Trying to reinstall XP with the above mentioned IRQ-measures:
installation denied with the error-message about a non ACPI-compatible
BIOS. Once I strike the VideoAction from the system or replace it with
DV Action Pro: All works perfectly, ACPI is fully supported.

Hercules support cannot recreate the problem - they say, the card
works within an ACPI environment.
But how can a system work fully under ACPI, and only create problems,
when this card is inserted?
I would more than appreciate to be helped to solve this problem.