Problema con procedimiento y paso de parametros

[MaMu]

En la sección Trucos, me topé con este interesante truco para obtener cualquier thumbnail de la Shell, funciona perfecto, pero no logro adaptar un string a PWideChar, como para pasarle los parametros por variables, siempre me tira error, alguna idea?

Código Delphi [-]
 
uses ActiveX, ShlObj, ComObj;
type
 IExtractImage = interface ['{BB2E617C-0920-11d1-9A0B-00C04FC2D6C1}'] // http://msdn2.microsoft.com/en-us/lib...48(VS.85).aspx
  function GetLocation(pszPathBuffer: LPWSTR; cchMax: DWORD; 
 var pdwPriority: DWORD; const prgSize: SIZE; dwRecClrDepth: DWORD; 
 var pdwFlags: DWORD): HRESULT; stdcall;
  function Extract(var phBmpImage: HBITMAP): HRESULT; stdcall;
 end;
function GetThumbnail(lpPathName, lpFileName: PWideChar; Width, Height: Integer): TBitmap;
var
 Desktop, Folder: IShellFolder;
 ItemIDList: PItemIDList;
 Flags, Priority: Cardinal;
 ExtractImage: IExtractImage;
 Res: HRESULT;
 hBitmap: Windows.HBITMAP;
 Buffer: array[0..MAX_PATH-1] of WideChar;
 Size: TSize;
begin
 Result := nil;
 SHGetDesktopFolder(Desktop);
 if LongBool(Desktop.ParseDisplayName(0, nil, lpPathName, PDWORD(0)^, ItemIDList, PDWORD(0)^)) then Exit;
 Desktop.BindToObject(ItemIDList, nil, IShellFolder, Folder);
 CoTaskMemFree(ItemIDList);
 if LongBool(Folder.ParseDisplayName(0, nil, lpFileName, PDWORD(0)^, ItemIDList, PDWORD(0)^)) then Exit;
 Folder.GetUIObjectOf(0, 1, ItemIDList, IExtractImage, nil, ExtractImage);
 CoTaskMemFree(ItemIDList);
 if not Assigned(ExtractImage) then Exit; // TODO
 Size.cx := Width; Size.cy := Height; Priority := 0;
 Flags := $28{IEIFLAG_SCREEN+IEIFLAG_OFFLINE};
 Res := ExtractImage.GetLocation(Buffer, SizeOf(Buffer), Priority, Size, 24{pf32bit}, Flags);
 if (Res = NOERROR) or (Res = E_PENDING{IEIFLAG_ASYNC}) then
  begin
   if not LongBool(ExtractImage.Extract(hBitmap)) then
    begin
     Result := TBitmap.Create;
     Result.Handle := hBitmap;
    end;
  end;
end;