DriverStudio 3.2

[boot loader]
timeout=15
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /noguiboot /NoExecute=AlwaysOff /noPae
multi(0)disk(0)rdisk(1)partition(1)\WINDOWS="Windows XP Professional x64 Edition" /fastdetect /noguiboot

It disables the DEP successfully and the /nopae is just there out of desperation.
Go figure why it doesn't turn off

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.

Kennus, it seams to be all right with your boot.ini
I have no idea :-(

I think, it is time to switch to DS3.2 ;-)