Alohaguy,
As far as I know, the lanacfg.exe is not dependent on the service pack. I have a system with XP2, and I never had any issues. Is you customer using Netbeui? Why not switch them to TCP? As this is the default protocol for XP, it's lana is usually zero as a default setting. It would serve as an effective workaround if you can't change the lana number.
Btw, the lanacfg.exe is not an Aloha utility, it's a MS utility. IF I am wrong, and there is a second one for SP2, you should be able to obtain it via MS website.