Реестр. String to HKEY

const
  HKEYNames: array[0..6] of string =
    ('HKEY_CLASSES_ROOT', 'HKEY_CURRENT_USER', 'HKEY_LOCAL_MACHINE', 'HKEY_USERS',
    'HKEY_PERFORMANCE_DATA', 'HKEY_CURRENT_CONFIG', 'HKEY_DYN_DATA');

function HKEYToStr(const Key: HKEY): string;
begin
  if (key < HKEY_CLASSES_ROOT) or (key > HKEY_CLASSES_ROOT+6) then
    Result := ''
  else
    Result := HKEYNames[key - HKEY_CLASSES_ROOT];
end;

function StrToHKEY(const KEY: string): HKEY;
var
  i: Byte;
begin
  Result := $0;
  for i := Low(HKEYNames) to High(HKEYNames) do
  begin
    if SameText(HKEYNames, KEY) then
      Result := HKEY_CLASSES_ROOT + i;
  end;
end;