If you receive the subject (or similar) message when you attempt to boot, or receive Press a key to reboot, your C: drive, the primary partition on your first drive, is not marked as the active boot partition.
An ERD will not fix the problem as it has no mechanism to mark a partition active.
To resovle the problem:
1. Boot from a Boot Floppy.
2. Use Disk Administrator to mark the partition active.
NOTE: If you don't have a Boot Floppy, you may be able to use FDISK.EXE by booting from a MS-DOS diskette.