Should Get An External Hard Drive

I wonder should I suggest my boss to buy an external hard drive for my computer or not. My computer is the main computer for our accounting and stock system software. I am worry that if I am accidentally downloads and install the software that might contain spyware or virus; I might destroy my company accounting system as well. That is what I worry the most. Since is impossibly for me to totally avoid download software from internet, then may get another external hard drive to store those important documents and file will be a good solution too.