You have reformatted a harddisk formerly used by a linux-system of some sort.
What you see is the remnant of an old Lilo boot record.
Use a DOS-diskette to start the machine, do fdisk /mbr and start your installation again from scratch.
The 'fdisk' command with the '/mbr' switch erases the master boot record so it's free for your new installation.
A damned annoying problem, but easy to solve, once you know the cure.