Автор: http://www.swissdelphicenter.ch

uses
  Psapi, tlhelp32;

procedure CreateWin9xProcessList(List: TstringList);
var
  hSnapShot: THandle;
  ProcInfo: TProcessEntry32;
begin
  if List = nil then
    Exit;
  hSnapShot := CreateToolHelp32Snapshot(TH32CS_SNAPPROCESS, 0);
  if (hSnapShot <> THandle(-1)) then
  begin
    ProcInfo.dwSize := SizeOf(ProcInfo);
    if (Process32First(hSnapshot, ProcInfo)) then
    begin
      List.Add(ProcInfo.szExeFile);
      while (Process32Next(hSnapShot, ProcInfo)) do
        List.Add(ProcInfo.szExeFile);
    end;
    CloseHandle(hSnapShot);
  end;
end;

procedure CreateWinNTProcessList(List: TstringList);
var
  PIDArray: array[0..1023] of DWORD;
  cb: DWORD;
  I: Integer;
  ProcCount: Integer;
  hMod: HMODULE;
  hProcess: THandle;
  ModuleName: array[0..300] of Char;
begin
  if List = nil then
    Exit;
  EnumProcesses(@PIDArray, SizeOf(PIDArray), cb);
  ProcCount := cb div SizeOf(DWORD);
  for I := 0 to ProcCount - 1 do
  begin
    hProcess := OpenProcess(PROCESS_QUERY_INFORMATION or
      PROCESS_VM_READ,
      False,
      PIDArray[I]);
    if (hProcess <> 0) then
    begin
      EnumProcessModules(hProcess, @hMod, SizeOf(hMod), cb);
      GetModuleFilenameEx(hProcess, hMod, ModuleName, SizeOf(ModuleName));
      List.Add(ModuleName);
      CloseHandle(hProcess);
    end;
  end;
end;

procedure GetProcessList(var List: TstringList);
var
  ovi: TOSVersionInfo;
begin
  if List = nil then
    Exit;
  ovi.dwOSVersionInfoSize := SizeOf(TOSVersionInfo);
  GetVersionEx(ovi);
  case ovi.dwPlatformId of
    VER_PLATFORM_WIN32_WINDOWS: CreateWin9xProcessList(List);
    VER_PLATFORM_WIN32_NT: CreateWinNTProcessList(List);
  end
end;

function EXE_Running(FileName: string; bFullpath: Boolean): Boolean;
var
  i: Integer;
  MyProcList: TstringList;
begin
  MyProcList := TStringList.Create;
  try
    GetProcessList(MyProcList);
    Result := False;
    if MyProcList = nil then
      Exit;
    for i := 0 to MyProcList.Count - 1 do
    begin
      if not bFullpath then
      begin
        if CompareText(ExtractFileName(MyProcList.Strings[i]), FileName) = 0
          then
          Result := True
      end
      else if CompareText(MyProcList.strings[i], FileName) = 0 then
        Result := True;
      if Result then
        Break;
    end;
  finally
    MyProcList.Free;
  end;
end;

// Example 1: Is a Exe-File running ?

procedure TForm1.Button1Click(Sender: TObject);
begin
  if EXE_Running('Notepad.exe', False) then
    ShowMessage('EXE is running')
  else
    ShowMessage('EXE is not running');
end;

// Example 2: List running Exe-Files

procedure TForm1.Button3Click(Sender: TObject);
var
  i: Integer;
  MyProcList: TstringList;
begin
  MyProcList := TStringList.Create;
  try
    GetProcessList(MyProcList);
    if MyProcList = nil then
      Exit;
    for i := 0 to MyProcList.Count - 1 do
      ListBox1.Items.Add(MyProcList.Strings[i]);
  finally
    MyProcList.Free;
  end;
end;