Not entirely true...I unplug my mouse/keyboard while its on, it still works if I plug it back in rightaway, however if you unplug it before BIOS detects it, then it will be unusuable and you would have to Re-Post. In the OS, it doesn't matter.PS2 is not plug and play, it was in use years before there was such a thing, unplug a mouse, then plug it back in, it won't keep working. I've seen many fried ports, only 1 board that might have died from it though. I certainly don't suggest removing and plugging with the power on. These aren't like usb guys. This problem is almost always with mice, keyboards will "plug and play" usually but not on all systems.