Accessing LocalApplicationData Equivalent in Delphi

Question

Using Delphi, how do I access the equivalent of .NET's System.Environment.SpecialFolder.LocalApplicationData variable (which works on any version of Windows)? I assumed I could just do:

dir := GetEnvironmentVariable('LOCALAPPDATA');

This works on Vista but XP doesn't seem to set that environment variable by default at least on my test machine.