@MarkusO:
I already posted this in an other thread, but it hasn't been posted here yet, so here it is again:

Maybe you have BIOS settings for this problem. I once worked with a 8x Xeon MP computer with 16 GB RAM installed and its BIOS contained a setting like (I don't remember the exact words): "enable memory hole above 4G". When you enabled it, Windows wasn't able to detect more than 4 GB of RAM. Although I don't know if this had an effect on the PAE settings.

I didn't yet install DS 3.2 (I only update when a protector "needs" it or when I reformat my HDD), so I can't tell you what happened to the variable you mentioned.

@willii:
I think MarkusO has no conflicts with DEP since he is using SP1a, but DEP was introduced in SP2. He already wrote that he, even if not using SP2, used the BOOT.INI setting "/NoExecute=AlwaysOff", which is identical to "/Execute".