I'm sure the magnetic field that these fans produce is far too small to be of any significance to the hdd(s). After all the Empeg team did toy with the idea of installing a fan (hence the holes in the lid). I think the reason they didn't go ahead was only because they felt that the player didn't need it and not for any risk from the magnetic field produced by the fan. As a little side note if you dismantle a dead (or alive for that matter if you're feeling sadistic) hard drive you'll find some Neodymium Iron Boron magnets which are extremely strong (and fragile). These are used to create a field that the head positioning coil can react against. Although these magnets are mostly enclosed in a Steel cage I'm sure some of the magnetic field leaks out and that this leakage amounts to more than the fan could ever produce. This is only my assumption though. There are some interesting experiments you can do with these magnets (most of which I haven't tried myself). One thing I have tried is to get two Aluminium plates spaced apart about 6mm to form a kind of hollow sandwich and drop one of these magnets through the gap. It seems like it's falling through Treacle. The falling magnet induces Eddy currents in the Ali plates. These Eddy currents create their own magnetic fields which react against the magnet's field slowing it's fall. If you do experiment with these magnets just make sure you keep them away from any Credit Cards, Monitors and any type of magnetic media.