This document discusses different types of computer viruses and provides tips to prevent viruses. It describes three main types of viruses: file infectors, boot sector viruses, and Trojan horse viruses. It notes that Windows XP deals with viruses more seriously and recommends using antivirus programs to protect systems. Two specific tips provided are to be careful with floppy disks which are a main virus source, and to exercise caution when downloading files from the internet. It also stresses the importance of keeping antivirus programs and virus libraries up-to-date, as over 100 new virus strains are released each month.