[R.i.m.s.k.y.]

Snap_Suzun, как то так

Код:

[Setup]
DefaultDirName={code:Path|{pf}\appp}

[*Code]
function Path(String: String): String;
var s1, path : string;
begin
path := ExpandConstant('{pf}\appp');
if RegQueryStringValue(HKCU, 'Software\www', 'Path', s1) then path := s1;
end;