Solved! Basicaly I had problems with all players and editors I tried. Now it seems it's fixed. I think my system was sort of in a mess. I had other issues (errors, programs non functioning etc) non related to wmv or multimedia which obliged me to reinstall windows and I had thousands of problem reinstalling it and reinstalling drivers which for no reason were uninstalled during the windows reinstall (crashes, BSODs, everything). Now it seems it's bcak to normal. Big disapointement for me: My installed file checker script were of no use in this case... (I think i'v been victim of virus while trying a freeware).