I recommend you type in "Game booster 2.2 activation key" into a search engine such as google, many sites claim to have cracks for Gamebooster. Its better if you do it because you can properly check which websites you trust, what links seem legitimate, ect... Instead of someone blindly posting a link.
Good luck, and take proper caution.
You can search on Google on these crack sites.
But I recommend you use TuneUp Utilities, it really helped here when I was using it.