oh, sorry,... here is my fault - itĀ“s been a while, so I have wrong memory here
as far as I remembered the scanner was shown in paintNet on 32bit just with twainable without driver... WHICH IS IMPOSSIBLE
for the 64bit machine, I definitely have no driver installed- that must be the point..
so the latest driver I can find is for Windows XP 32bit (2007)
I should install this one and try twainable+, right?