Answer:
Computer viruses can harm your computer in MANY ways! Some of the most common kinds and effects of viruses are:
Repetitive Launch: From the time you boot up, your computer slows down at a faster and faster rate.
BIOS Corrupting: This kind plays games with your computer's core programs.
Lockup: This kind causes your computer to lockup almost right away.
Screen Cover: This kind virtually covers your screen with an image or video. This can make it look as if your computer is unresponsive.
OS Deletion: This kind systematically deletes your entire Operating system (example: it will empty your entire Windows folder).
Random Deletion: This will randomly delete files on your computer.
Other: There are other kinds as well, that are not as common.