I know you have the answer but your subject made me look closer. I am successfully running exactly your combo except for the all-important XP/SP2 (I'm Win2K/SP4).
Thanks, you put another nail to never upgrade to XP.
I didn't run SP2 for the longest time. till the tech desk at my work installed it as part of a new image for other software to function properly. I really would like to keep Kerio since it gives me that much more control by using the packet filter compared to ZA. -- "Knowledge is contagious, infect"