SOLUTION for user who cannot install DT4!!!

[Copytrooper]

This issue is not a question of ACPI or StandardPC. I've v4 installed in XP both ACPI and StandardPC without any problems, although in StandardPC XP five devices share the same IRQ. The other way around even ACPI PCs have this problem, too.
It seems to be a problem of BIOS and hal.dll which is still under investigation.

[Dafko]

Ive tryed few IRQ without any solution

[Stevo34]

I doubt Standard PC or Uniprocessor PC makes a diff.
My PC was already Uniprocessor.
I have had the device problem 12 error for the last two weeks.
After pulling out many hairs there was only one answer left... reinstall windows.

Make sure ACPI is enabled in your BIOS then reinstall windows. A windows repair did not work for me but it may for you.
Make sure you back up important files like e-mails!

Note:-
This also fixed another problem I had.
My PC would not turn off by itself after shutdown.
I used to get the message "It is now safe to turn off your computer."
PC now turns off by itself!
This tells me it must be important to install XP with ACPI enabled in BIOS. (Avoid resource conflicts and more)

Thanks Team for a great release. Works a charm.
Worth my time reinstalling windows!