If your Dell laptop has a headphones jack but no line-out jack can you still connect a 5.1 surround sound speaker system to it?

You can connect the 5.1 speaker system to the dell laptop as long as the cable is not an optical or digital cable. Some cables double analog or digital. These you can use. You should be able to plug them in if the connector fits. You may not have sound out of all of your speakers but you can still try. If the plug will fit then nothing can be hurt. If it does not work you might try getting an external usb sound card(e.g. soundblaster mp3) I hope that answers your question.