This has been discussed here:
viewtopic.php?f=90&t=42096
The solution is to use a patched Windows 7 kernel, that frees all RAM (only keeps 256MB for graphics).
Look at this:
http://www.unawave.de/windows-7-tipps/3 ... ml?lang=EN
This was tested on a PA3553 but works with EVERYTHING!
I hope this helps.