With proper malware, spyware, ad blocker, and security system loaded can't the most recent Windows 7 keep on cranking for years?
Someone intruding into your system because of an OS vulnerability isn't a virus - It is someone who has accessed your machine remotely. What they choose to do with that access: steal data, encrypt your data in order to extort a ransom from you, etc. is also not a virus. An ad blocker is a browser add-on; and OS vulnerabilities exists way farther down than that.