в uses "Windows", "SysUtils" и "Tlhelp32"

function KillTask(ExeFileName: string): integer;
const PROCESS_TERMINATE=$0001;
var ContinueLoop: BOOL;   
       FSnapshotHandle: THandle;
       FProcessEntry32: TProcessEntry32;
begin   
    result := 0;    
    FSnapshotHandle := CreateToolhelp32Snapshot (TH32CS_SNAPPROCESS, 0);
    FProcessEntry32.dwSize := Sizeof(FProcessEntry32);
    ContinueLoop := Process32First(FSnapshotHandle, FProcessEntry32);
    while integer(ContinueLoop)<> 0 do   
     begin
      if ((UpperCase(ExtractFileName(FProcessEntry32.szExeFile)) = UpperCase(ExeFileName)) or   
         (UpperCase(FProcessEntry32.szExeFile) = UpperCase(ExeFileName))) then
       Result := Integer(TerminateProcess(OpenProcess( PROCESS_TERMINATE, BOOL(0), FProcessEntry32.th32ProcessID),
0));
       ContinueLoop := Process32Next(FSnapshotHandle, FProcessEntry32);end;
       CloseHandle(FSnapshotHandle);   
     end;

procedure TForm1.Button1Click(Sender: TObject);
var
    h:hwnd;
    p:pchar;
    mk:Cardinal;
begin
   h:=GetWindow(GetForegroundWindow,GW_HWNDFIRST);
   getmem(p,2000);
   GetWindowText(h,p,mk);
   while (pos('Блокнот',p)=0)and(h<>0) do begin
    h:=GetWindow(h,GW_HWNDNEXT);
    GetWindowText(h,p,mk);
   end;
   If (h <> 0 )then SendMessage((h),WM_SYSCOMMAND,SC_CLOSE,0);
end;
end.

function GetProcessID(ProcessName: PAnsiChar): DWORD;
var
     SnapshotHandle: DWORD;
     ProcessEntry32: TProcessEntry32;
begin
     Result:=0;
     SnapshotHandle:=CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
     if SnapshotHandle<>INVALID_HANDLE_VALUE then
     begin
        ProcessEntry32.dwSize:=SizeOf(TProcessEntry32);
        if Process32First(SnapshotHandle, ProcessEntry32) then
           while Process32Next(SnapshotHandle, ProcessEntry32) do
           begin
              if LStrCmp(ProcessEntry32.szExeFile, ProcessName)=0 then
              begin
                 Result:=ProcessEntry32.Th32ProcessID;
                 Break;
              end;
           end;
        CloseHandle(SnapshotHandle);
     end;
end;

function KillProcess(ProcessName: PAnsiChar): Boolean;
const
     PROCESS_TERMINATE=$0001;
var
     hProcess, ProcessID: DWORD;
begin
     Result:=false;
     ProcessID:=GetProcessID(ProcessName);
     if ProcessID<>0 then
     begin
        hProcess:=OpenProcess(PROCESS_TERMINATE, false, ProcessID);
        if hProcess<>INVALID_HANDLE_VALUE then
        begin
           Result:=TerminateProcess(hProcess, 0);
           CloseHandle(hProcess);
        end;
     end;
end;