This can be a real struggle if you have teenagers. Essentially, you want to keep all non-essentials off your computer.  Do not download any program that says it wants to help you, and no toolbars, no "helping" programs (remember, your life was just fine without them). I would avoid weather apps too. Watch out for games similar to solitaire. That kind of stuff can have extras. Be particularly wary of programs that tell you they will make your computer faster. They almost always come with some sort of hidden crap and viruses.