Your problem is honestly one of the strangest on record. Please ensure you are not running a 32-bit operating system. To do this, try opening a command prompt by going to:
Start -> Search -> cmd
In the command console type "systeminfo" and press enter. Scroll up to find:
"System Type: x64-based PC"
(While there are other ways to obtain this information, this would seem to be a quick and reliable way).
I would recommend, also, going into System Information, by going to Start -> Search -> msinfo32.exe
If you are comfortable revealing system information, export your information as a text file and attach it to a post in this thread. The information in this file will contain what Windows recognizes on your system a fairly fine degree, but will not compromise security information such as the product keys, etc.
I would also recommend that, during this process, you identify whether or not your OS is picking up on all of the memory modules. A good system diagnostics and reporting software is AIDA64:
Downloads | AIDA64 You can use a 30 day trial just to collect as much information as possible on what could be the cause of this problem. However, memory allocation in Windows 7 64-bit should not be the cause of the problem. It is much more likely that a severe misidentification of some component is the cause (i.e. human error). All of this is conjecture right now, because, quite honestly, without identifying the cause, that is always a likely culprit.
I would go so far as to suggest that you really do follow these steps, if only for your own benefit, and to get to the bottom of this problem. Again, this problem is mostly seen on 32-bit systems that are trying to utilize >4GB of RAM. In that instance, Windows can never allocate more than 4GB, and a certain amount of RAM, usually .5-.75GB under the 4GB hard limit, is reserved for allocation of graphics card memory. If you are using 64-bit Windows, you should not have any reserve memory allocation problem.
If you can completely rule out that you are using 32-bit Windows, this looks like a hardware problem. DIMM slots could even be damaged or have something in the slots blocking contact with the modules. Carefully check for hardware errors by removing the memory after fully powering down and disconnecting the system. Sometimes, on rare occasions, when installing new DIMMs, you may encounter a problem whereas if power is not fully drained from the board, or if there is an electrical discharge when installing the memory, the DIMM slots or RAM can be damaged beyond repair. To rule out a problem in this area after a hardware inspection, you're going to want to create a Memtest bootdisc and test your RAM. See also:
Memtest86+ - Advanced Memory Diagnostic Tool If you come to believe that one of the DIMM slots or RAM modules may be damaged, you should start cycling memory, one-by-one, into various configurations on the motherboard. This is best done by testing each RAM module on DIMM SLOT 1 and DIMM SLOT 3 (for tri-channel configurations) after first testing all modules on DIMM1. Go ahead and slowly expand until you have all of your RAM slots occupied once again and have ruled out any damage to each module. Eventually, you may discover a problem with one of the DIMMs.
My main problem with this solution itself, however, is that the memory is posting. The reason why the operating system may not be able to recognize more than 3.25GB still eludes me, but there have been occasions whereas when a DIMM slot itself was damaged, I found that Windows would recognize all of the memory, but only show some available. In fact, one DIMM slot on a tri-channel board may still be reporting, with another one damaged. This would explain why, if you have 2x2x2, you see 4GB and the OS cannot allocate >3.25GB. While this is a long shot, it is a situation I have seen play out before, sometimes with 16GB reported and only 8GB or 4GB usable. The fact that it is "3.25GB" still eludes me.
Try all of these steps, but for the most part, extensive testing is going to be required to resolve this problem. Unless of course you are running 32-bit Windows. My opinion would be, based on all information presented, that this is a partial motherboard failure that may have taken place when you installed the additional RAM or a problem with the RAM itself. Try to remember if you banged or dropped the RAM before installing it, or if any questionable incident may have taken place that may have fried any of the components.
Any further information you can provide will be useful in moving forward. It would be especially useful if you post on the issue if you have already managed to resolve it somehow.