A chatbox like IM box appeared on my screen and started chatting with me. Said they have been watching me for awhile and basically they want me to use Paypal to pay them money, they said they have seen me use it before. I did not reply when they asked for money and I shut everything down. I went back online last night for awhile and nothing came up. Everything seems to work fine on my laptop and I have not heard from them again. I have run spybot and malwarebytes and tried to clean with those two programs, but I don't know what to do now. How can I get rid of it and how can I ever be sure that they are gone and can't get back in so that I can use my laptop again and feel secure.