Well, I deleted last copy and downloaded again, this time after doing all recommended Windows updates. Download appeared OK, first attempt was interrupted somehow, so I did it again. On trying to open (clicking on downloaded file, it asked to be Unzipped, did so to a new folder. After that, a brief screen pops up every time I try to open, saying "Radiant...exe has stopped working" "Windows is checking for a solution" and then screen disappears. I've asked Mark for a disc, to see if that will work.