If you got a connector you could rob 12v from the pc's power supply, black gnd and yel +12, the solenoid would be ok for just a blip, just put a back emf diode across the coil to prevent any back emf upsetting the pc.
You could use a transistor and a relay to drive the relay coil from the port (or even drive the solenoid coil direct), or if you want even simpler you might be able to drive a reed relay directly from the port, check the current capability of the port is enough to provide the relay with enough mA.
Someone here probably knows.