Dear Evie,
Thanks for the answer. I found the log file: after multiple unsuccesful install attempts (trying both the online and the offline installer) it is still completely empty. It is named Installer_20150226.txt.
There are no trace in the event viewer of these unsuccessful installations. One event might be relevant, this is the XML error file:
<Event xmlns="__http://schemas.microsoft.com/win/2004/08/events/event__">
<System>
<Provider Name="__Windows Error Reporting__" />
<EventID Qualifiers="__0__">1001</EventID>
<Level>4</Level>
<Task>0</Task>
<Keywords>0x80000000000000</Keywords>
<TimeCreated SystemTime="__2015-02-26T22:49:07.000000000Z__" />
<EventRecordID>13499</EventRecordID>
<Channel>Application</Channel>
<Computer>BHNBUDIME.bhn.kme.intern</Computer>
<Security />
</System>
[-](file:///C:/Users/HUBU1093/AppData/Local/Temp/tmp930.xml#) <EventData>
<Data>1557438147</Data>
<Data>5</Data>
<Data>RADAR_PRE_LEAK_WOW64</Data>
<Data>Nem érhet? el</Data>
<Data>0</Data>
<Data>installer.exe</Data>
<Data>0.0.0.0</Data>
<Data>6.1.7601.2.1.0</Data>
<Data />
<Data />
<Data />
<Data />
<Data />
<Data />
<Data />
<Data>C:\Users\HUBU1093\AppData\Local\Temp\RDR6A63.tmp\empty.txt</Data>
<Data />
<Data />
<Data>0</Data>
<Data>a70581b0-be09-11e4-99b3-534e57000000</Data>
<Data>0</Data>
</EventData>
</Event>
However, I dont always get this event after installations. : (
Any and all help would be much appreciated.