I was phoned by someone saying they were from the technical department of my broadband supplier. I foolishly let them enter my computer (Acer Aspire 5732Z). When I realised it was a scam call and disconnected it, they retaliated by blocking access to the computer. I now get a box saying I nee this to to enter startup password. Of course I do not have this. How can I bypass this start up the laptop?