[gogomanu]

When I said "I solved the problem" I was talking about my computer not seeing the mp4 as an ADFU device in the taskbar (only as an S1MP3 ADFU Driver in the Device Manager). That was simple to solve...I updated the ADFU Driver and selected "No,not this time - Install from a list or specific location - Don't search, I will choose the driver to install". And then in the window that appeared (Compatible hardware) there were "S1MP3 ADFU" Driver and "USB 2.0 (HS) ADFU Device". I chosed the second one, and that was it.
Sorry if I made you missunderstand...The MAIN problem is still unsolved, but this site really gives me hope. Thanx again for your work