Thx for answering JanB,
but the problem has to do with the system memory, as far as i know this is completely indepent of the cache of the diskstorage cache.
I do have a 256 GB SSD as primary disk, that means that i cannot use the so called " ready boost" option with a memory stick, because w7 switches this off on fast systems.
It also has no connection with the cache inside blender, the cache there is used for renderings and animation inside blender.
It has to do with the exporter PyPRP1 , because that exporter seems not to flush data during its export.
It seems to keep its data until the very very end, where it finally writes the " sum" and " fni" file.
I noticed that it seems better not to use the option to pack textures inside Blender.
I used to do that if i want to share Blendfiles.
But the unpacking of the file seems to happen inside the exporter again. This adds another amount of internal used memory.
The memory use seems to decrease with a " clean" relative path to the used texture.
It would be nice if it is possible to just add single objects without a complete export.(1 export of the current age is more then 1 hour!)
It must be possible somehow, but i do not understand how to do it.
The system tray in w7 is indeed a "memory munger" .
I did use dropbox a few times for filesharing and its always opened in there.
Closing this down completely , gives me 1 Gbyte more memory space available.
VLC streaming is another one.
And yes, it worked again!
I just finished a new fresh export!
It took 1518 seconds because the Texcache already existed.