I am a new user of a 998cSI. I have recorded a sonar run but was surprised to find that HumminbirdPC does not replay the recordings. I have now downloaded Humviewer. However, it does not seem able to open the files that I recorded. If I open the RECORD folders there are two kinds of file .IDV and .SON, but Humviewer steadfastly refuses to open either type. As there do not seem to be any instructions with Humviewer it is difficult to work out what I am doing wrong. Any ideas?