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

function ProcessExists(exeFileName: string): Boolean;
var
    ContinueLoop: BOOL;
    FSnapshotHandle: THandle;
    FProcessEntry32: TProcessEntry32;
begin
    FSnapshotHandle := CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
    FProcessEntry32.dwSize := SizeOf(FProcessEntry32);
    ContinueLoop := Process32First(FSnapshotHandle, FProcessEntry32);
    Result := False;
    while Integer(ContinueLoop) <> 0 do
    begin
      if ((UpperCase(ExtractFileName(FProcessEntry32.szExeFile)) =
        UpperCase(ExeFileName)) or (UpperCase(FProcessEntry32.szExeFile) =
        UpperCase(ExeFileName))) then
      begin
        Result := True;
      end;
      ContinueLoop := Process32Next(FSnapshotHandle, FProcessEntry32);
    end;
    CloseHandle(FSnapshotHandle);
end;

procedure TForm2.Button1Click(Sender: TObject);
begin
  if processExists('notepad.exe') then KillTask ('notepad.exe');
end;