>What does it mean when OS() returns "Windows 5.00"?
>The OS is Win/NT 4.0 (I'm not sure which SP). VFP is 6.0.
>On the same workstation, it returns "Windows NT 4.00" when running the VFP development product, but under the runtime, it is returning "Windows 5.00".

Is Windows 2000 anywhere in the scheme? Like maybe it's a COM server sitting on a Windows 2000 server? VFP just makes a Win32 call to determine the OS version, so VFP wouldn't report what you're seeing unless it's sitting on a Windows 2000 box.