@jameswoodcock .. and even before W95 Defrag, Norton Utilities had a defrag utility for Windows and Dos. I'd watch that for hours (while studying)

If anyone wants this in W10/11, Defraggler from Piriform (CCleaner) have a free edition. It too has the block by block data move representation. Problem is disk drives are so big these days that each block in the display is hundreds or thousands of logical device blocks, so often times you'll see just two or three blocks light up. Not as exciting.