Speaking about upgrades, my iMac got a very special upgrade: 12 GB of RAM, a second screen, and a backup hard disk.
Second screen was already known, but this time with a way to proof it.
Since Windows 7 says only 3,9 GB out of the 4 GB is usable, it means you're using the 32-bit version of Windows 7.
All 32-bit OS's (Windows, BSD, Linux), and all 32-bit Apps (most Apps available) are limited to 4 GB of RAM only, while 64-bit doesn't have limits yet.
Then forget what I've said.
It's based on the fact, that most people I know have 4 GB of RAM, but can only use 3,40 GB, because they have a 32-bit Windows.
The funniest part is, it has nothing to do with regions.
Here's something Microsoft wrote:
http://msdn.microsoft.com/en-us/library/windows/desktop/aa366778(v=vs.85).aspx#physical_memory_limits_windows_7
Additionally, this is why it happens:
http://hardforum.com/showthread.php?t=1035670