...
const
  URL_POST = 'hots.ru/uploadtest.ashx';
...
procedure POSTFile(Filename: String);
var
 TotalDataCount, i: Integer;
 IdHTTP: TIdHTTP;
 LPostStream: TIdMultiPartFormDataStream;
 LResultStream: TStringStream;
 LpostString: String;
 function PostDecode(AString: String): String;
 begin
  Result := CharReplace(AString, '%', ' ');
  Result := CharReplace(Result, '&', ' ');
 end;
begin
 IdHTTP := TIdHTTP.Create(nil);
 try
  IdHTTP.MaxLineLength := 0; //koi8-r windows-1252
  LPostStream := TIdMultiPartFormDataStream.Create;
  LpostString:= FileToString(Filename);
  LPostStream.AddFormField('UserData', PostDecode(LpostString));
  LResultStream := TStringStream.Create('');
  try
    try
      IdHTTP.Post(URL_POST, LPostStream, LResultStream);
    except
      on E:Exception do
      begin
        Showmessage(E.Message);
      end;
    end;
    showmessage(LResultStream.DataString);
  finally
    LPostStream.Free;
    LResultStream.Free;
  end;
 finally
  IdHTTP.Free;
 end;
end;

string x = "sdsdsd";
System.IO.File.WriteAllText(@"c:\text1.txt", x);