If your sound card doesn't have a loopback, check this free virtual sound input/output:
http://vb-audio.pagesperso-orange.fr/Cable/index.htm.
Configure ableton to output in the virtual cable input and then use the virtual cable output in Lightjams. In the Windows sound recording panel, configure the virtual cable output to also output to your speakers if needed. Click the properties button then go in the listen tab, check the "listen to this device" box and select your speakers in the drop down box.