I'm trying to record with the Boss GT-10 into my laptop, but I can't hear what I'm playing through the speakers. I tried using the USB interface, but I couldn't get it to work. Does anybody have any advice on how to remedy this problem?

The mic monitor or "stereo mix" as it used to be called was renamed. It's also going to be loaded with latency and not worth using.

It is definitely well worth your time to figure out the USB connection so that you can use the device as an external soundcard or at least a proper source of audio. This may also allow you to use some other output on the device for monitoring the stream without the latency associated with a trip through your computer first.

Whenever you're tempted to plug something (other than a gaming headset mic) into a computer's mic in: stop and think about it first; it's going to be the wrong idea nine times out of ten.

Thanks for the feedback, I'll try to figure out how to use USB connector.