Hello WhoCares 
Thank you for your fast reaction. However, I’m not out of trouble yet.
3 I did your suggestion 3, but it doesn’t solve the problem yet.
4 I read a very lot of different anti-virus-programmes ans spy-bot-like-programms in the answers, but they are mostly dealing with other variants of DyfucDldr, such as B,A and F, so I do not yet know if that is the solution.
5 Googles virus-search-database seems to have never heard of DyfucDldr
6 I was already using spybot 1.3 and there are no more recent updates available.
7 I hope you have some additional tips and tricks ? 
Thx Fred