Hmm I apparently didn't explain it well.

I run Vista Ultimate 64 and that was not the reason why I got myself PE Explorer :D

I used that tool to change the flag (you also can use EditBin) for Poser 7 to use more than max 2 or 3 GB. Because it doesn't use more than that without the changed flag. Reason why I started all this fuss :-/

Now Poser 7 uses during my more complex scenery renders about 3,8 - 3,89 GB of RAM.
Even if I had 8 GB, Poser 7 can't be forced to use more than max. 4 GB...

Too bad. I wonder why they do not create 64 bit versions that work with much more RAM than now.