From what I have seen in other threads, some users with Windows 7 have the same problem. Namely they find themselves, like me, locked on the "Neverwinter" screen. But it seems to be a "known issue" => http://www.arcgames.com/en/forums#/discussion/1200194/strongholds-issues
My graphic drivers are up to date, I installed them yesterday. So this is not the problem.