Código Delphi [-]
library Injection;

uses
  Windows, Sysutils, Messages, Psapi, CommCtrl;

type
  TShared = record
    Hook: HHooK;
    AttachCount: Integer;
  end;
  PShared = ^TShared;

  PItem = ^TItem;
  TItem = record
    hWnd: HWND;
    WndProc: Pointer;
    Next: PItem;
  end;

var
  Mutex, Mem: THandle;
  Shared: PShared;
  Injected: Boolean;
  HandleList: PItem;

function FindWindowProc(hWnd: HWND; Item: PItem): Pointer;
begin
  if Item <> nil then
  begin
    if Item.hWnd = hWnd then
      Result:= Item.WndProc
    else
      Result:= FindWindowProc(hWnd,Item.Next);
  end else
    Result:= nil;
end;

function WindowProc(hWnd: HWND; Msg: UINT; WParam: WPARAM; LParam: LPARAM):
  LRESULT; stdcall;
var
  Str: String;
begin
  if (Msg = WM_SETTEXT) then
  begin
    Str:= String(PChar(LParam));
    Str:= StringReplace(Str,'1,00 GB','2,00 GB',[rfReplaceAll,rfIgnoreCase]);
    Str:= StringReplace(Str,'512 MB','1,00 GB',[rfReplaceAll,rfIgnoreCase]);
    LParam:= Longint(PChar(Str));
  end;
  Result:= CallWindowProc(FindWindowProc(hWnd,HandleList),hWnd,Msg,WParam,lParam);
end;

procedure HookWindow(hWnd: HWND);
var
  Item: PItem;
begin
  if FindWindowProc(hWnd, HandleList) = nil then
  begin
    GetMem(Item,Sizeof(TItem));
    Item.hWnd:= hWnd;
    Item.Next:= HandleList;
    Item.WndProc:= Pointer(SetWindowLong(hWnd,GWL_WNDPROC,LongInt(@WindowProc)));
    HandleList:= Item;
  end;
end;

function CallWndProc(Code: Integer; wParam: WPARAM; lParam: LPARAM): LRESULT;
  stdcall;
var
  ClassName: array[0..16] of Char;
begin
  if Code = HC_ACTION then
    if Injected then
    begin
      FillChar(ClassName,Sizeof(ClassName),0);
      if GetClassName(PCWPStruct(lParam).hwnd,@ClassName,Sizeof(ClassName)-1) > 0 then
        if StrIComp(ClassName,'Link Window') = 0 then
        begin
          HookWindow(PCWPStruct(lParam).hwnd);
        end;
    end;
  Result := CallNextHookEx(Shared^.Hook, Code, wParam, lParam);
end;

procedure StartHook; stdcall;
begin
  if Shared <> nil then
  begin
    WaitForSingleObject(Mutex, INFINITE);
    try
      with Shared^ do
      begin
        if Hook = 0 then
          Hook := SetWindowsHookEx(WH_CALLWNDPROC, @CallWndProc, HInstance, 0);
      end;
    finally
      ReleaseMutex(Mutex);
    end;
  end;
end;

procedure StopHook; stdcall;
begin
  if Shared <> nil then
  begin
    WaitForSingleObject(Mutex, INFINITE);
    try
      with Shared^ do
      begin
        if Hook <> 0 then
        begin
          UnhookWindowsHookEx(Hook);
          Hook := 0;
        end;
      end;
    finally
      ReleaseMutex(Mutex);
    end;
  end;
end;

procedure Inject;
var
  Process: THandle;
  ModName: array[0..MAX_PATH] of Char;
  Target: array[0..MAX_PATH] of Char;
begin
  Injected:= FALSE;
  Process := OpenProcess(PROCESS_QUERY_INFORMATION or PROCESS_VM_READ, FALSE,
    GetCurrentProcessId);
  if Process <> 0 then
  begin
    if GetModuleFileNameEx(Process, 0, ModName,sizeof(ModName)-1) > 0  then
    begin
      FillChar(Target,Sizeof(Target),#0);
      GetSystemDirectory(@Target,Sizeof(Target)-1);
      StrLCat(Target,'\rundll32.exe',Sizeof(Target)-1);
      OutputDebugString(Target);
      if StrIComp(Target,ModName) = 0 then
      begin
        // Un pequeño pitido nos avisa de que no hemos infiltrado
        Windows.Beep(500,100);
        HandleList:= nil;
        Injected:= TRUE;
      end;
    end;
    CloseHandle(Process);
  end;
end;

procedure Attach; stdcall;
var
  isNew: boolean;
begin
  Mutex := CreateMutex(nil, True, '{92366DA1-4F66-472D-BE12-65F0993F62AC}');
  try
    Mem := CreateFileMapping($FFFFFFFF, nil, PAGE_READWRITE, 0, SizeOf(TShared),
      '{D1A38D62-9FAB-4298-A358-579D2D286E40}');
    isNew := GetLastError() = 0;
    if Mem <> 0 then
      Shared := MapViewOfFile(Mem, FILE_MAP_WRITE, 0, 0, 0)
    else
      Shared := nil;
    if Shared <> nil then
      if isNew then
        with Shared^ do
        begin
          Hook := 0;
          AttachCount := 1;
        end
      else
        inc(Shared^.AttachCount);
  finally
    ReleaseMutex(Mutex);
  end;
  // Aqui viene la inyeccion
  Inject;
end;

procedure UnHookWindows(Item: PItem);
begin
  if Item <> nil then
  begin
    UnHookWindows(Item.Next);
    SetWindowLong(Item.hWnd,GWL_WNDPROC,LongInt(Item.WndProc));
    FreeMem(Item);
  end;
end;

procedure Detach; stdcall;
begin
  WaitForSingleObject(Mutex, INFINITE);
  try
    if (Shared <> nil) then
      dec(Shared^.AttachCount);
  finally
    ReleaseMutex(Mutex);
  end;
  if (Shared <> nil) then
    if Shared^.AttachCount <= 0 then
    begin
      StopHook;
      UnmapViewOfFile(Shared);
      CloseHandle(Mem);
      CloseHandle(Mutex);
    end;
  if Injected then
    UnHookWindows(HandleList);
end;

procedure DLLEntryPoint(Reason: integer);
begin
  case Reason of
    Dll_Process_Detach: Detach;
    Dll_Process_Attach: Attach;
  end;
end;

exports
  StartHook,
  StopHook;

begin
  Attach;
  DLLProc:= @DLLEntryPoint;
end.