Windows 7 64bit cutting ram in half

Hello,
I have been dealing with this issue for a while now. I installed 8gb of ram, and was running Ubuntu all was fine and dandy, but for work i need windows for most things, so i did a nice fresh install on another hard drive. I was doing some work one day when i saw windows say "8gb install (3.99gb usable)" Now the installation is legit and 64 bit. I started doing research, found people having this issue but most where solved by bent cpu pin or settings in bios. Now my ram is 4 sticks, and two different brands/speed. The timings are all the same 9 - 9 - 9 - 24 , the Corsair set was 1600 @ 1.65v and the Patriot was 1333 @ 1.5V. I messed with all the settings and resets until I was blue in the face, but nothing fixed the problem. So I just lived with it, until today when i pulled out the corsair sticks or ram for another project. Now I booted up windows and saw "4gb installed (1.99gb usable)" . Has anyone else ever had this issue ????? I have been working on and building computers all my life and never have encountered this. I have a dedicated graphics card, its some cheap GT 520. Im just really confused. Thanks !

How many programs are running on your computer? to check you go to ALT/CTRL/DELETE Start Task Manager then click the performance tab, if your CPU usage is high find the program which is using the Memory and uninstall it, to check what program is using it go to the services tab.

According to task manager total physical memory 2gb. The data I have posted was from the system manager. this is not ram being used, this ram available to use.

Download CPU-Z and that tells you the proper DRAM Frequency, my Winodws says I have 1600Mhz but CPU-Z says I have 1070.2MHz.

I have had that installed, and it tells me that my ram modules are installed, I checked when I had 4 modules installed and all info was correct. ram running at 667mhz. Now i have two and it still says all the correct info.

Are you memory sticks corsair vengeances?