If, even after you read all the information above, you are still determined to give Happy Guitar a look and a try, you can download it just from here. All you need is a Windows operating system and Flash Player ActiveX installed (you can download it here as well). For full experience a working guitar is recommended, as well as a microphone connected to the computer where Happy Guitar will be installed.
That's it, the software is and absolute freeware, you can do with it whatever you want, you can disassemble it, you can destroy it, you can use it, you can copy it, you can send it to Microsoft, you can give it to your grandparents as a present, whatever comes to your mind... But first you have to download it, from here: