I had one 8GB stick of RAM installed under Windows 7 (32bit) but it only said 3.93 GB was usable out of the maximum 4GB allow under 32bit Operating Sysyems. However, now I have upgraded to Windows 7 64bit with two 8GB sticks but it only shows 8GB installed and 7.86GB of RAM usable.

I tried the following but it did not help:

Click Start , type msconfig in the Search programs and files box, and then click msconfig in the Programs list.
In the System Configuration window, click Advanced options on the Boot tab.
Click to clear the Maximum memory check box, and then click OK.
Restart the computer.

Any advice?