If you get a virus then just use maleware bytes to remove it.. That's all. It's very unlikely one will just randomly pop into your system destroying your data and killing the parts without you actually doing something to allow it such as clicking on ads. Most of the time it's usererror of them clicking random stuff then it is just random unluckyness.
If one gets in, you run a scan and remove it, and then move on
I doubt skype, msn, yahoo spreads viruses. I use all 3 and have been fine for months. Are you talking about the file transfer stuff?
Not to be rude but in my opinion you're overeacting the whole virus thing. People get them and remove them everyday, most are useless troll viruses anyhow.