Ниже идёт пример "крякера" для игры Hidden and Dangerous. Он как раз пишет в реестр.

program setupreg;
{$APPTYPE CONSOLE}
uses
Windows, Registry, SysUtils;
Const
I3D : array [1..16] of byte = ($e4,$f7,$49,$21,$af,$c3,$d4,$93,$54,$a0,$47,$b7,$4a,$68,$16,$3b);
Var
Reg : TRegistry;
begin
Writeln('Hidden and Dangerous 1.0 registry patcher');
Writeln('CopyLeft 2001 by [TAHK]Executioner, [TAHK]BACEK');Writeln;
Write('Patching... ');
Reg := TRegistry.Create;
Reg.RootKey := HKEY_LOCAL_MACHINE;
if Reg.OpenKey('\SOFTWARE\Insanity3D system\Access data', True) then
begin
Reg.WriteBinaryData('Validate check', I3D, 16);
Reg.CloseKey;
end;
if Reg.OpenKey('\SOFTWARE\Take2\Hidden and Dangerous\1.00', True) then
begin
Reg.WriteInteger('Install type',0);
Reg.WriteString('Install dir',GetCurrentDir+'\');
Reg.DeleteValue('Insanity 3D');
Reg.CloseKey;
end;
Reg.Free;
Writeln('well done!'); Writeln;
Write('Enjoy now!'); Readln;
end.