This KB is taken from some old microsoft archive, mirrorred on https://jeffpar.github.io/kbarchive/kb/066/Q66530/
Back in the ancient MS-DOS days, If you did not SYS right after FDISK and FORMAT, you could well end up with a "No Room for System on Destination Disk" error.
In one case, it turned out I had to use a 4.0 MS-DOS Bootable disk with SYS to reallocate enough disk space for the OS. I do not use 4.0 otherwise because it's a memory hog, but I could then SYS from a 3.3 MS-DOS, without reformatting! Neat.