I belive if you want to use system() then you need to include stdlib.h, not windows.h.

For strings, you can also do it this way:

#include <iostream>
using namespace std;

int main()
{
char *username;
cout << "enter your name: ";
cin >> username;
cout << endl << "hello " << username << " you are very cool";
return 0;
}
If this doesn't work... Someone tell me. I haven't programmed in C++ for a while and I might have forgotten something .