Как сделать, чтобы запускалась только одна копия приложения?

Code:

begin

if HPrevInst <> 0 then

   begin

     ActivatePreviousInstance;

     Halt;

   end;

end;

Code:

unit PrevInst;

interface

uses

WinProcs,

WinTypes,

SysUtils;

type

PHWnd = ^HWnd;

function EnumApps(Wnd: HWnd; TargetWindow: PHWnd): bool; export;

procedure ActivatePreviousInstance;

implementation

function EnumApps(Wnd: HWnd; TargetWindow: PHWnd): bool;

var

ClassName: array[0..30] of char;

begin

Result := true;

if GetWindowWord(Wnd, GWW_HINSTANCE) = HPrevInst then

   begin

     GetClassName(Wnd, ClassName, 30);

     if STRIComp(ClassName, 'TApplication') = 0 then

       begin

         TargetWindow^ := Wnd;

         Result := false;

       end;

   end;

end;

procedure ActivatePreviousInstance;

var

PrevInstWnd: HWnd;

begin

PrevInstWnd := 0;

EnumWindows(@EnumApps, LongInt(@PrevInstWnd));

if PrevInstWnd <> 0 then

   if IsIconic(PrevInstWnd) then

     ShowWindow(PrevInstWnd, SW_Restore)

   else

     BringWindowToTop(PrevInstWnd);

end;

end.