I was looking at the Windows file defragmentation APIs recently and it made me want to write something that uses them. Not a defragmentation tool necessarily (there are tons of those, and with the advent of SSDs they're becoming irrelevant anyway). But maybe something for visualizing how directories, files and other structures are laid out on disk. At one pixel per sector, this would make for a very big bitmap (~25000 pixels square for the 300Gb drive I use for data on my laptop and ~75000 pixels square for the largest 3Tb drives) so I'd have to make a way to zoom in and out of it. And how should I arrange the sectors within the bitmap? Row major is the obvious way, but a Hilbert space-filling curve might make for nicer results. For colouring, I was thinking of using the file extension as a hint (e.g. red for images, green for audio, blue for video, grey for binary code, yellow for text, black for free space) and maybe making the first sector of a file brighter or darker so that you can see if it's one big file or lots of small ones (though weighting the sector by how much of it is used would have a similar effect). I also want the program to show which sector of which file is under the mouse pointer.