Hoaxes are usually silly pranks, and are a form of chain mail, and are often also Urban Legends.

Computer Virus hoaxes try to generate fear, uncertainty and doubt (FUD) into the recipients, bringing them to believe that there is an 'undetectable virus' on their system (how can it be undetectable if it can detect it ?).

Some have actually been malicious in content, causing the recipient to delete files from their systems.

They should simply be deleted.

There is no good luck from sending them to 20 of your friends, nor are they a way in which you will learn anything about the security of your computer.