Pezzz is absolutely correct when he says; "" Internet Explorer " ... The number one browser.... For downloading a better browser....." IE actually provides the highest number of badly created bits of software which are designed to force the reader into looking at stuff they REALLY don't want or need to see!!!, it almost invites invasive programs onto your machine!! PLEASE don't use it! I use Firefox, which is good, I have also used Chrome but I find it too thin a program, they advertise it as being a very light-weight browser and it is...too light weight! I also used to use Opera for a while but it got too fat and dumb to keep going.
You also need an effective firewall program operating in the background, I use ZoneAlarm Extreme, have done for some years and have never had a single really nasty virus from day one! It has trapped the few that tried, told me about them after it locked them up before they can actually do anything, and then it has asked me what I'd like to do with them. Even some instances where it can't immediately remove them, in these cases it has locked them away until the next time the machine is re-booted, then it's kicked them off as part of the power-up process. It's not free by any means, but it is painless to use and extremely effective!! It protects my basic machine, scans the Internet before I get to access anything (not that I notice any extended time periods), locks the backdoors for the machine, scans emails and all other messages for nasty's, and deals with them instantly. Current downloads are tested as part of the store and locked away if there is any problem at all.
Well worth the annual fee, give it a whirl!