Scary Experience

I plugged in four external drives to my PC today, and suddenly a bunch of messages started popping up in the taskbar. Terrifying messages like 'the data on K:/public_html/cyberd.org/ could not be saved. This might have to do with hardware malfunction'. They kept on appearing, so I opened up the drive (onscreen), and half the data was GONE. O_o Since my computer is old and does mess things up at times I switched off all external drives and plugged back in only the one with memory loss, and it had no memory loss no more, phew, divine relief. Tried plugging in all drives at the same time again, same problem. It seems one of the drives is conflicting with this one, which is strange, shouldn't be happening, but without that specific drive everything works fine (and it's not a limit on the number of drives plugged in by USB, I've had five connected earlier with no trouble). Searched Google but it doesn't seem like anyone else has had this problem, let me know if you have.