Thank you, Whappo, for your prompt answer, I have tried both of them. I had some problems with that freeware fairuse when installing it, it didn't install correctly and I needed to unistall it and reinstall it. Finally it did install but I couldn't manage to convert my wmv files properly, meaning after conversion I had a green vertical line on the videos.
Meanwhile I have tried also Tunebite, of course it's free version which only allowed me to convert just 1 min from a file. But with this one didn't have any problem, I followed all the steps in installation and then when I started it immediately detected my protected files from pc. Too bad this one is a paid one but I'll playing with it around and download some music and see how it really works. Maybe I'll buy the paid one.
Too bad that free fairuse didn't work, as I said I need something easy to use and not too complicated, for me this one begun to be complicated in the moment it didn't installed properly but it crossed my mind to unistall it and try again.
Anyway thank you a lot