I have found a great library to solve this:
https://mega.co.nz/#F!RcQkhSxI!_ZsnpdapAeoVVWEgVw2iMQ
using WinTB v2.0 you can easily turn on the preview on the Taskbar:
#include "WinTB.iss"
[Setup]
AppName=Wintb.dll example
AppVersion=2.0
DefaultDirName={pf}\Wintb.dll example
DefaultGroupName=Wintb.dll example
OutputDir=.
[files]
Source: wintb.dll; Flags: dontcopy;
[code]
procedure InitializeWizard();
begin
ExtractTemporaryFile('wintb.dll');
Win7TaskBar11();
end;
without any external plugin or dll, it can be solved by this trick:
[Code]
function SetWindowLong(Wnd: HWnd; Index: Integer; NewLong: Longint): Longint; external '[email protected] stdcall';
function GetWindowLong(Wnd: HWnd; Index: Integer): Longint; external '[email protected] stdcall';
Function GetWindow (HWND: Longint; uCmd: cardinal): Longint;external '[email protected] stdcall';
procedure InitializeWizard();
begin
SetWindowLong(WizardForm.Handle, -8,GetWindowLong(GetWindow(WizardForm.Handle, 4),-8));
end;