just plug in the 3.5mm to stereo RCA cable from your pc speaker to the philips dvd player.

FYI, all the sounds ouput from that stereo out RCA connection will be in stereo. even though the source is in Dolby or dts 5.1, it'll be downmixed automatically be the player to stereo.

even the LFE and bass from all the channels will be compressed into that stereo signal...delivered and played on your pc speaker.