If it was real strong it might do something.
Ever placed a normal magnet next to a floppy disc? Buh-bye data.
Same thing would happen if you could get a strong enough magnetic field next to a hard drive. Floppies are covered in plastic, hard drive usually have metal casings. The metal casing provides more protection from such things.
I wouldn’t recommend trying it, but doing so would provide us with a real world test.