Can I get some help with Mobireader problems on 8700?

Hi Guys
Just wondering if anyone could help me. I have an 8700 which I love and has mobipocket reader on it. I have Windows 8.1. Unfortunately I cannot get mobireader destop to let me add it as a new reading device. Each time I try a box comes up telling me to install Blackberry Desktop but I already have this program on my computer and it shows my phone connected whilst I am trying to add my 8700 as a reading device. There is no SD card on my phone and so using mobireader is the only way of getting new books on it. I had no problem with my previous laptop. Many thanks.

So the real problem is Windows 8.1 and mobireader?
8.1 has issues with a lot of apps. What about going to the website for the app and asking for help there?