Thank you Murr44, I actualy have this one, but it seems it's doing a very poor job on the Registry section of it.
I think I actually found an efficient one there :
http://www.eusing.com/free_registry_...ry_cleaner.htm
Thank you very much for your help.
That said, and even after a registry cleaning, and replacing the msvcr71.dll, I still have the same problems mentionned above : mosaique like screen when Alt+Tab, or " Spiel Beenden".
Have to disconnect puter from main and boot again. Dont know what's causing that...

JMV.