Every now and then i defrag my HDD partitions to maintain my PC, and each time i notice fragmented files that i haven't read/wrote-to in a while. For example npm-cache, i haven't used Node for ages!
I have Windows Search disabled, and i can't think of any action or application that would randomly read random files on my HDD, all that uses my HDD on Idle are uncharted system processes, constant and small read/writes.
What causes unused files to get fragmented?