This is a family of at least 11 small, non-interesting viruses, which add their code in front of any files they infect.
Allow F-Secure Anti-Virus to disinfect the relevant files.
For more general information on disinfection, please see Removal Instructions.
An extremely badly written variant, which crashes on many machines.
This 301 byte variant activates in September and displays the text:
Sad virus - 24/8/91