>>>...In my opinion, a DesignReview and a AutoCAD LT installation is enough to open DWG-files?...<<<
You have LT2013 installed, why use ADR to open DWG files? You answered your own question so to speak. Just wondering.
>>>...Now I try to open a DWG File with Design Review 2013...<<< ADR is not designed to open DWG files, all it does is find a default setting (and a program) to convert to DWF first: is that what you want, to randomly and uncontrollably have another program translate a DWG file to a generic DWF file to view? Wouldn't it be better if you deliberately created a DWF file on your own chosing and your own set parameters first? Very atypical and random behavior is being sought here, with no control.
Has LT2013 been used to open DWG files? Is LT2013 the default program to open DWG files on the system?