Epubor Ultimate installed smoothly and quickly on Windows 10 Professional. I tried converting a random .MOBI to .PDF and a random .PDF to .MOBI. Both the conversions were successful, although the PDF output was rather better quality. The only real problem that I could see was that the “drag and drop” functionality, which totally dominates Epubor Ultimate’s user interface, didn’t work at all – and I’ve never had any kind of problem with d&d before. Even so the program is much quicker to launch and use than Calibre, so it’s a keeper. Many thanks to Epubor and SOS.