Hello!
My problem is;
Recording in Stereo is not working.
I get only Mono. Same signal in both channels.
Using Laptop Aspire V3-571 and Lenco USB Turntable L-3867-USB.
NOTICE.
It is working on my other computer Fujitsu/Siemens,
with Windows XP.
I hope you can help me.
Bo Örtenvik
I have the same problem on my new laptop with windows 10. I have bought yesterday an Asus X540S, installation is ok but when I started using audacity I have a problem over the audio. It is working on my Sony vpcea21fx that is running in windows 7.
If you really have the same problem (whatever it is that you want to record does so in mono), then apply the same solution that Steve mentioned. Here is our FAQ about recording in stereo that might make it clearer: http://manual.audacityteam.org/man/faq_recording_how_to_s.html#rinstereo.
If you need more help after that, tell us exactly what you are trying to record, and the makes and model numbers of the recording equipment, and we’ll move this to a new topic to avoid confusing the original poster.
Gale
Sorry for the confusion Gale I followed Steve instruction very well. I think the problem is not about the software. The problem is that my new computer have been a corrupted audio files and need to be reprogram again that’s what it said to the store where I bought my laptop. So sorry for the confusion, but truly thanks for the response. Really appreciate it so much! I Bookmarked the FAQ page that you send and will make it a reference when I got a problem over my recording before asking for help here. Thanks! 
I’ll mark this topic [SOLVED] then and lock it assuming you can now record in stereo. I recommend starting a new topic if you have any more questions, with details specific to your own problem.
Gale