C: windows, often used software (fastest SSD) d: personal storage organised by type(folder), e: client files organised by client/project (future modifications get a new project folder), reference files have their own folder inside the client/project they are associated with.

More generic references go onto my personal drive.

I have it this way due to losing a ton of old work when I lost a hd, since then client files on their own drove that I backup online regularly. If I lose my personal/games drive it's no big deal to re download.