Viruses are most common in shareware. Actually, to the contrary, shareware is very rarely infected. The shareware industry polices itself very effectively and there have been only a few isolated incidents of virus infected shareware being distributed to a vast number of people. I heard the xxxxx virus will destroy my yyyyy. Not physically, not in the sense that you'll have to throw any components into the trash can.
Viruses can only wreak havoc on data.
There is no virus that has ever crumpled disks, melted processors, caused a monitor to spontaneously combust, put Nair in your shampoo or Rogaine in your Nair. Making my files read-only protects them from viruses. File attributes can be by executable programs. Anything an attribute utility can do, a virus can undo. CD-ROMs and write protected floppy disks are safe.