I knew it would come to this - same experience about a year ago.
Looking for a solution to a problem, Regservo advertisement offers the solution with a free scan which immediately found several hundred problems with the traditional fix of several of them and a full cure once the money is paid. While still thinking it over things started going wrong necessitating the purchase in desperation. Needless to say things did not improve despite online conversations with a guy named Matt.
Paypal was informed but were unable to extract any money from them. Furthermore a complaint was lodged with a department apparently affiliated with the FBI but also no feedback.
I wound up purchasing Kaspersky with a five day scan getting everything back to normal.