Try one of these:
file_get_contents('http://users.ign.com/about/'.$name);
file_get_contents("http://users.ign.com/about/$name");
PHP doesn't interpolate the string for variables if it is in a single quote. It will with a double quote.
Also, yes, it will only work with register_globals set to on, as it looks like you have it. Try this (assuming your are using the post method with the form)
$name = $_POST['name'];