I have a PS Audio Nuwave DAC can I play DSD files through Windows 7 and JRiver software
Not without converting them to PCM files. I haven’t tried it but apparently JRiver can do that on the fly. See http://wiki.jriver.com/index.php/DSD_Format
If you try to play them on JRMC it will ask you if you want to proceed with the downsampled file. All good. You will have to get a new DS to play dsf files like you get from Acoustic Sounds without the need to downsample.