If you've ever stopped by a Diskeeper booth at a trade show in the past few years, you may have seen our clear-case PCs.
Inside those clear case PCs we have WD Raptor X drives with a see-through cover. That clear cover allows you to watch the disk head moving across the platter.
When you defragment one drive and leave one fragmented, it makes for an interesting visual side-by-side comparison. That's a test we videoed and posted on YouTube.
Defragmented drives, mean less wear and tear over the life of the drive so it lives longer. It also means less energy used to power and cool the PC.