Thanks for thinking with me. However, the online info explicitely states that when using the Clear option, only the registry settings of the current version (in this case 3.10) will be influenced. I could nevertheless try it but I’m afraid I’ll end up with a version 3.10 that doesn’t work either.
I think I’ll wait for a clarification from Plextor, and I hope it will be something useful. First they tell me I should install a version that doesn’t exist and then that I should change registry settings using a program that doesn’t start. By the way, it’s not the first irrelevant response I get from them.
Finally, I keep wondering why they sell a software version 3.10 that isn’t the last one and why the automatic s/w update function of this program, which is acclaimed to be one of the program’s advantages, says that there is no update available.
I get excellent burns with my drive but the joy is somewhat diminished by the sloppy service surrounding it. I’m glad there is this forum! 
Lou