I just responded to an email fro JRiver to prepurchase MC32. I assumed that this was for Mac, and on the purchase page I chose the version for MAc. What I was able to download was a MJR file. I've never before seen this extension. When I try to open it, I'm directed to a link to the Forum. Did I accidently download a file intended for Windows? If not, how am I supposed to install this app?