I installed PEP1 (I never upgraded to PEP 2 or 3) on Windows 10 machine a few years ago without problems. Only downloading to Pronto TSU9400 did not work. I then have to install Windows XP on my retro computer and used that without problems, downloading worked fine. Now today I read this thread and installed Net Framework 3.5 (includes .NET 2.0 and 3.0). Now downloading to TSU9400 works fine!

The funny thing is that installing Pronto software worked without problems or errors but only downloading to remote did not work without Net Framework 3.5.

When I connected TSU9400 to USB 3.0 Hub it did not download anymore. It only worked connected to computers own USB port (which is also USB 3). Weird. I am still happy that dowloading is now working.