Copy from my post at Moddb:
Found an unnofficial CoC v1.4.22 Windows XP patch. Works fine so far. I checked out the changes and it is just the version check in the PE header inside xrEngine.exe: Change two bytes in xrEngine.exe at offset 0x170 and 0x178: both from value 06 to 04; the whole package then runs in Windows XP.
Why did I not find this a week earlier?...
Also works with v1.5Beta-R4.
One limitation: 'Trucks Cemetery' will fail to load lacking memory. Even at the very lowest setting, even with most textures removed from the game.