due to a big bug in the system and due to the huge problems during and after several re-installations from the original DVD, i decided to try windows 8.1 system. i found some translation bugs in the german version of win 8.1 so i tried the english version which works perfect
first step is to move c:\oem hidden folder to the sd drive, otherwise you are not able to install e.g. office later on
then you download iso image from microsoft site http://windows.microsoft.com/en-us/windows-8/preview-iso
i saved the image also to the sd card because of lack of space on my c: drive
then you click to the iso image and the virtual drive e: will be open. run setup.
choose "nothing" to be left on hard disk and wait about 90 min.
and this is all. at the end you will get a new system installation on your tablet.
btw, in spite of other's earlier experiences, no need of mouse, no problem with wifi or even touchscreen driver.
the office installation file you will find deep in your c:\oem saved folder under setuphomestudentretail.x86.xx-xx where xx means your language version
would be nice to know your experiences
thanks