MG stands for "Matematicheska Gimnazia", the name of the school in Varna in Bulgaria where the virus seems to have been written. MG hides itself in the upper half of the interrupt table, causing programs like Netware to crash. Several variants are known, and have been named MG-1, MG-2, etc.
Allow F-Secure Anti-Virus to disinfect the relevant files.
For more general information on disinfection, please see Removal Instructions.