It would be pretty easy to model and 3d print an adapter to fit a Pi into a 3.5HDD bay. You'd have to run the power and Ethernet connection out the back of the

It would be pretty easy to model and 3d print an adapter to fit a Pi into a 3.5HDD bay. You'd have to run the power and Ethernet connection out the back of the PC through a water cooler grommet or PCI slot, but it would give the pi a safe home with good air flow! I considered doing this once for a file server I was hosting on a pi (since it would provide a home for a storage drive as well), but ended up going a different route.