I currently use a PC Line USB mouse on an XP system. I need to go back to a PS/2 mouse in preparation to use a KVM, but when I plug such a mouse in it doesn't respond. The device is visible, but doesn't respond. I've uninstalled the USB mouse, but still the PS/2 mouse won't work. Strangely, after an uninstall of the USB mouse, I can plug it back in to a running system and it works ok. I can't see anything in Start Up, but could there be something running at system start up to make the USB mouse the active device ?