编译通不过，咋办？

#include "stdafx.h"
#include "iostream.h"
#include  <string>
using namespace std;


int main()
{
    string x="7";
    string y="&";
    x+=y;
    x+="8";
    cout<<x<<endl;
}

编译出现如下提示：C:\Documents and Settings\Administrator\桌面\357357357\357357357.cpp(16) : error C2679: binary '<<' : no operator defined which takes a right-hand operand of type 'class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char>
 >' (or there is no acceptable conversion)