I must be really stupid but when I run: eg. "Sndview FATBOY.asf" the message just says corrupt sound file. How can I change this?

Check what version of sndview you have. If it is 0.32 this automatically selects the decoder option. This does not work properly. If you do have this version reply back and I will email Sndview 0.31 which i used to convert the .ASF files to .WAV