I've got portableapps.com installed on my D: drive, and I've noticed that all the new data -e.g. after a program updates- gets written to the back of the disk, effectively spacing things out and making the arms on the drive work harder. It sounds like it's doing more searches, and then the browser page loads will get a bit slower, and I'll remember to defrag. That fixes it by stacking everything closer together.
Is this by design? Can I turn it off? Am I missing something?