sony vaio ps2 problem

we are having a problem with a sony vaio pcg f270 laptop. when we plug in a optical or regular external mouse with the computer shut off, and then power up the computer here is what happens. the second we move the external mouse multiple programs open and continue opening until we force the computer to shut down. if we power up the computer and plug the external mouse in it works as well as the touchpad mouse at the same time. is this normal? do we just have to remember to power up the machine first before we hook up the external mouse? we are using windows 98se. thank you , paul