TDownFile做下载，下载的EXE文件用不了，为什么?(100分)

我做了一个程序，程序中调用了别人做的一个下载涵数，下载的文本文件能打，但EXE文件打不出，高手帮我看一下
///////////////////////////////////////////////////////////////////////////////
unit U_TDownFile;
interface
uses SysUtils, Windows, UrlMon, ActiveX,Classes,shellapi;
type //下载流量状态回调接口类
TOnProgressEvent = procedure(ulProgress, ulProgressMax, ulStatusCode: integer;szStatusText:String) of object;
TOnCompleteEvent = procedure(Source_file,Dest_file:String;blStatus:boolean;ErrMessage:String) of object;
TBindStatusCallback = class(TObject, IBindStatusCallback)
protected // IUnknown
FRefCount: Integer;
function QueryInterface(const IID: TGUID;
out Obj): Integer;
stdcall;
function _AddRef: Integer;
stdcall;
function _Release: Integer;
stdcall;
public // IBindStatusCallback
FProgress : TOnProgressEvent;
FComplete : TOnCompleteEvent;
function OnStartBinding(dwReserved: DWORD;
pib: IBinding): HResult;
stdcall;
function GetPriority(out nPriority): HResult;
stdcall;
function OnLowResource(reserved: DWORD): HResult;
stdcall;
function OnProgress(ulProgress, ulProgressMax, ulStatusCode: ULONG;szStatusText: LPCWSTR): HResult;
stdcall;
function OnStopBinding(hresult: HResult;
szError: LPCWSTR): HResult;
stdcall;
function GetBindInfo(out grfBINDF: DWORD;
var bindinfo: TBindInfo): HResult;
stdcall;
function OnDataAvailable(grfBSCF: DWORD;
dwSize: DWORD;
formatetc: PFormatEtc;stgmed: PStgMedium): HResult;
stdcall;
function OnObjectAvailable(const iid: TGUID;
punk: IUnknown): HResult;
stdcall;
end;

TThreadDown =class(TThread) //下载线程类。
private
Source_file : string;
Dest_file : string;
StatusCallback : TBindStatusCallback;
protected
procedure Execute;
override;
public
constructor Create(URL,FileName: String ;
StatusCB: TBindStatusCallback);overload;
end;

TDownFile=class(TComponent) //文件下载控件
private
FOnProgress: TOnProgressEvent;
RevedByte : TBindStatusCallback;
FOnComplete: TOnCompleteEvent;
procedure SetOnProgress(const Value: TOnProgressEvent);
//下载进度
procedure SetOnComplete(const Value: TOnCompleteEvent);
//下载完成
public
constructor Create(AOwner: TComponent);reintroduce;
destructor Destroy;
reintroduce;
procedure ThreadDownFile(Source,Dest:string);
proceduredo
wnFile(Source,Dest:string);
published
property OnComplete:TOnCompleteEvent read FOnComplete write SetOnComplete;
property OnProgress:TOnProgressEvent read FOnProgress write SetOnProgress;
end;
implementation
{ TBindStatusCallback }
function TBindStatusCallback._AddRef: Integer;
begin
Inc(FRefCount);
Result := FRefCount;
end;

function TBindStatusCallback._Release: Integer;
begin
Dec(FRefCount);
Result := FRefCount;
end;

function TBindStatusCallback.GetBindInfo(out grfBINDF: DWORD;
var bindinfo: TBindInfo): HResult;
begin
Result := E_NOTIMPL;
end;

function TBindStatusCallback.GetPriority(out nPriority): HResult;
begin
Result := E_NOTIMPL;
end;

function TBindStatusCallback.OnDataAvailable(grfBSCF, dwSize: DWORD;
formatetc: PFormatEtc;
stgmed: PStgMedium): HResult;
begin
Result := E_NOTIMPL;
end;

function TBindStatusCallback.OnLowResource(reserved: DWORD): HResult;
begin
Result := E_NOTIMPL;
end;

function TBindStatusCallback.OnObjectAvailable(const iid: TGUID;
punk: IInterface): HResult;
begin
Result := E_NOTIMPL;
end;

function TBindStatusCallback.OnStartBinding(dwReserved: DWORD;
pib: IBinding): HResult;
begin
Result := E_NOTIMPL;
end;

function TBindStatusCallback.OnStopBinding(hresult: HResult;
szError: LPCWSTR): HResult;
begin
Result := E_NOTIMPL;
end;

function TBindStatusCallback.QueryInterface(const IID: TGUID;
out Obj): Integer;
begin
if GetInterface(IID, Obj) then
Result := S_OK
else
Result := E_NOINTERFACE;
end;

function TBindStatusCallback.OnProgress(ulProgress, ulProgressMax,
ulStatusCode: ULONG;
szStatusText: LPCWSTR): HResult;
begin
if Assigned(FProgress) then
FProgress(ulProgress,ulProgressMax,ulStatusCode,szStatusText);
Result := S_OK;
end;


//=============================================================================
{ TDownFile }
constructor TDownFile.Create(AOwner: TComponent);
begin
RevedByte:=TBindStatusCallback.Create;
inherited;
end;

destructor TDownFile.Destroy;
begin
RevedByte.Free;
end;

procedure TDownFile.SetOnComplete(const Value: TOnCompleteEvent);
begin
FOnComplete := Value;
if Assigned(FOnComplete) then
;
RevedByte.FComplete := FOnComplete;
end;

procedure TDownFile.SetOnProgress(const Value: TOnProgressEvent);
begin
FOnProgress := Value;
if Assigned(FOnProgress) then
;
RevedByte.FProgress := FOnProgress;
end;

procedure TDownFile.ThreadDownFile(Source, Dest: string);
var
ThreadDown:TThreadDown;
begin
ThreadDown:=TThreadDown.Create(Source, Dest,RevedByte);
ThreadDown.Resume;
end;

procedure TDownFile.DownFile(Source, Dest: string);
var
blDownOK:boolean;
ErrMessage:String;
begin
ErrMessage:='';
blDownOK:=false;
try
if UrlDownloadToFile(nil,Pchar(Source),Pchar(Dest),0,RevedByte)=0 then
blDownOK:=true;
except on e:exceptiondo
ErrMessage:=e.Message;
end;
if Assigned(RevedByte.FComplete) then
RevedByte.FComplete(Source,Dest,blDownOK,ErrMessage);
end;

//==============================================================================
{ TThreadDown }
constructor TThreadDown.Create(URL, FileName: String;StatusCB: TBindStatusCallback);
begin
Source_file := URL;
Dest_file := FileName;
StatusCallback := StatusCB;
FreeOnTerminate:=true;
inherited Create(true);
end;

procedure TThreadDown.Execute;
var
blDownOK:boolean;
ErrMessage:String;
begin
ErrMessage:='';
blDownOK:=false;
try
if UrlDownloadToFile(nil,Pchar(Source_file),Pchar(Dest_file),0,StatusCallback)=0 then
blDownOK:=true;
except on e:exceptiondo
ErrMessage:=e.Message;
end;
if Assigned(StatusCallback.FComplete) then
StatusCallback.FComplete(Source_file,Dest_file,blDownOK,ErrMessage);
end;

end.