I got the .rar file to open using Unpacker (found in Windows store as a freebie) in Windows 8.1. File still works fine using inches and feet as units of measure. Superimposed grids on walls, ceiling and floor assumed as one square foot in order to better locate your reflection points. Now on to the mid to high frequency trap builds. Good program...Very easy to use and understand. Side note: I always knew the reflection points described by this program would be problematic in my home theater: Now with this program I can visually see their locations - given my input data - to better deal with them using DIY acoustical traps. Thank you!!