Unlike most other boot sector viruses, Form infects the DOS boot sector on hard drives instead of the Master Boot Record. Form is only able to infect a hard disk when you try to boot the machine from an infected diskette. At this time Form infects boot sector, and after that it will go resident to high DOS memory during every boot-up from the hard disk. Once Form gets resident to memory, it will infect practicly all non-writeprotected diskettes used in the machine. Form will create bad sectors on disks it infects.
Form is one of the most widespread viruses in existance.
This is a pretty common minor variant of Form with no changes in the functionality.