>While I would expect the "only 3.25 GB are usable" with a 32-bit version of Windows 7 pro, I only have the x64 version.
You should have mentioned this first. That's the first thing I thought of.
The specs say it can have a max of 4 GB and that the CPU is capable of 64 bit. And graphics memory is shared with system memory, up to 128 MB. And nothing was mentioned about Windows 7.