Intergrate paypal's IPN (instant payment notification) on paypal account and PHP on steam.
Develop register and login system using MySQL Database and PHP.
Protect registration page with reCAPTCHA service.
Set up login system to existing application.
Set up account to lock to first computer used.
Set up subscription service based on price in MySQL accounts through paypal IPN
Set up self installing executable that creates shortcut and folder in program files