Know the risks and reduce or avoid the worst of them. So turn your computer on and be careful what you put in it. If not, you have to check it yourself. Ask your vendor to check that next time you buy a computer with software already on it. Never load software from a floppy disk onto your system without checking it first.
Accidents happen even to the big manufacturers.
If not, you have to check them yourself. Ask your manufacturer to check that next time you buy software. Beware of friends bearing floppies. You can't get a virus by looking at a text file or by reading a message on a BBS or other on-line service. Viruses only come from executing software.