There are already good solutions below. The one thing I would add is that this may not be a "silver bullet" kind of problem. I'd throw everything I can into the mix to create layers of protection. Educate them but also add software solutions to the mix.
A small addition, how often do they need to install new software after initial setup? Maybe take away admin privileges?
A small addition, how often do they need to install new software after initial setup? Maybe take away admin privileges?