Also if they suspect your system is already compromised, that could mean that you are infected with some rootkits or viruses which might not be detected by normal AVs. So I would even format the windows and do a clean install. Invest in some good antivirus. If you can't afford it, at least have Microsoft's security essentials.

Most important thing, use firefox or chrome with adblock. Other than the normal plugins, if any website wants you to install anything to be able to watch something, it could be bull. So try n avoid such websites. There are always others that are real.