But they tend to clutter up somewhat, but it's never fatal unless you mistreat it by installing malware or running too many background programs you don't need.
When I ask that question I'm actually refering the what makes an OS work I am not referring to any possible virus etc.
I've always used, and liked, XP pro for years. I've heard both good and bad about Windows 7 & 8 but I'm so used to XP I'd just as soon stick with what I know.
I had one IT type person who suggested that your operating system can get old and certain functions fail or hiccup. He suggested that a reinstall is good at least once a year and just copy of your original drivers and data (files).
Is that true that an OS can die from old age or" fatigue"?