Is the string null-terminated? If so, then you can use the `sf::String::String(const wchar_t*)` constructor (doc from [here](http://www.sfml-dev.org/documentation/2.1/classsf_1_1String.php#a5742d0a9b0c754f711820c2b5c40fa55)):
```cpp
joystickDescription = &productKey[0];
```