If you are experiencing latency issues, you may want to know that NCH recommends ASIO or Windows Core Audio for both playback and recording. ASIO and Windows Core Audio will provide the best performance and the lowest possible latency and offer the greatest accuracy when synchronizing recordings. ASIO will also allow you to play and record from multiple channels of the same device. If you don't have an ASIO capable sound card then you should choose Windows Core Audio as your playback and recording
option. Another option is to install the driver from ASIO4ALL which provides a layer over the regular soundcard, allowing it to be used as an ASIO device by software such as MixPad. You can download it for free from http://www.asio4all.com/
To mute a track, you just need to click the "M" button that you will see on each track.