uses
{$IFDEF WIN32}
 Registry; {We will get it from the registry}
{$ELSE}
 IniFiles; {We will get it from the win.ini file}
{$ENDIF}
{$IFNDEF WIN32}
const
 MAX_PATH = 144;
{$ENDIF}
function GetProgramAssociation(Ext: string): string;
var
{$IFDEF WIN32}
 reg: TRegistry;
 s: string;
{$ELSE}
 WinIni: TIniFile;
 WinIniFileName: array[0..MAX_PATH] of char;
 s: string;
{$ENDIF}
begin
{$IFDEF WIN32}
 s := '';
 reg := TRegistry.Create;
 reg.RootKey := HKEY_CLASSES_ROOT;
 if reg.OpenKey('.' + ext + '\shell\open\command',
  false) <> false then
 begin
  {The open command has been found}
  s := reg.ReadString('');
  reg.CloseKey;
 end
 else
 begin
  {perhaps thier is a system file pointer}
  if reg.OpenKey('.' + ext,
  false) <> false then
  begin
  s := reg.ReadString('');
  reg.CloseKey;
  if s <> '' then
  begin
  {A system file pointer was found}
  if reg.OpenKey(s + '\shell\open\command',
  false) <> false then
  {The open command has been found}
  s := reg.ReadString('');
  reg.CloseKey;
  end;
  end;
 end;
 {Delete any command line, quotes and spaces}
 if Pos('%', s) > 0 then
  Delete(s, Pos('%', s), length(s));
 if ((length(s) > 0) and
  (s[1] = '"')) then
  Delete(s, 1, 1);
 if ((length(s) > 0) and
  (s[length(s)] = '"')) then
  Delete(s, Length(s), 1);
 while ((length(s) > 0) and
  ((s[length(s)] = #32) or
  (s[length(s)] = '"'))) do
  Delete(s, Length(s), 1);
{$ELSE}
 GetWindowsDirectory(WinIniFileName, sizeof(WinIniFileName));
 StrCat(WinIniFileName, '\win.ini');
 WinIni := TIniFile.Create(WinIniFileName);
 s := WinIni.ReadString('Extensions',
  ext,
  '');
 WinIni.Free;
 {Delete any command line}
 if Pos(' ^', s) > 0 then
  Delete(s, Pos(' ^', s), length(s));
{$ENDIF}
 result := s;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
 ShowMessage(GetProgramAssociation('gif'));
end;