Since 1 week I have my PC back. I had questions, because in the service shop they had set up the wrong username...
http://forums.winamp.com/showthread.php?t=366832 Finally I have connected Winamp 5.7 Beta with Winamp Cloud again. I got duplicates of the media library playlists, but I have solved this problem, I just deleted them in Winamp and Winamp Cloud.
I see 2 PCs with the same name now in Winamp Cloud. The "dead" PC had nearly 20000 itmes (I had once over 20000 items in the media library). The "new" PC shows only nearly 3000 items in Winamp Cloud, although I have currently 7629 items in the media library of Winamp. I can only hope, that I will see more items in Winamp Cloud tomorrow, if not, then I have a problem. I also don't see in Winamp, which files I have already uploaded to Winamp Cloud. I don't want to start from scratch, because I needed so many hours for the uploading of the albums. Maybe I can simply upload new files, where I know, that I didn't upload them yet. I never wanted to have such a situation.
In Winamp I see no items in Local Library, it wasn't possible to load the "PC" and the Winamp Storage, only the media library itself is loaded very quickly. Because it's freshly connected, maybe it just needs more time (because it would take a while).
I will keep my eyes open and I will look tomorrow again...