Yep,. that is what the RCA connectors on the beolabs are for. Just switch them to Line and find a cord that goes from Minijack (in the computer) to 2 male RCA plugs, one for each speaker (left/right). Maplin should be able to supply such a cable.
best regards
Christian
Beosound Ouverture, Beocenter 9000, Beovision MX6000, Beocord VX7000