Help, Permanent Lag? useless noob lost in the world of computers!!

Firstly, sorry about all this rubbish but I've got to post it;

]Asus M5A99X EVO Rev 2 AMD 990X, S AM3+, DDR3, SATA III - 6Gb/s, RAID SATA, PCIe 2.0 (x16), ATX

AMD -FX 8120 3.10Ghz
AMD RADEON HD 6900 series
Corsair CMZ16GX3M4A1600C9B 16GB (4x4GB) 1600MHz CL9 DDR3 Vengeance Blu Memory Four Module Kit (should be 4x4.00gb only 2 running)
Corsair CX600 PSU
corsair force 3 SSd 120gb

OS Name Microsoft Windows 7 Ultimate
Version 6.1.7600 Build 7600
Other OS Description Not Available
OS Manufacturer Microsoft Corporation
System Name CHRIS1-PC
System Manufacturer To be filled by O.E.M.
System Model To be filled by O.E.M.
System Type x64-based PC
Processor AMD FX(tm)-8120 Eight-Core Processor, 3100 Mhz, 8 Core(s), 8 Logical Processor(s)
BIOS Version/Date American Megatrends Inc. 0901, 02/12/2011
SMBIOS Version 2.7
Windows Directory C:\Windows
System Directory C:\Windows\system32
Boot Device \Device\HarddiskVolume1
Locale United Kingdom
Hardware Abstraction Layer Version = "6.1.7600.16399"
User Name Chris1-PC\Chris 1
Time Zone GMT Daylight Time
Installed Physical Memory (RAM) 8.00 GB
Total Physical Memory 6.95 GB
Available Physical Memory 3.86 GB
Total Virtual Memory 13.9 GB
Available Virtual Memory 10.3 GB
Page File Space 6.95 GB


I built this PC last year with little idea what I was doing!

I use it for Autodesk / Skp / rendering.

some occasional gaming; skyrim / total war / BF3 etc..

From the outset I've have been unable to get 4x4GB of memory to work only 8gb. I previously posted a thread a while ago and tried the various solutions that were put forward to no avail including memtest/ bios settings / voltage/ checked compatability etc etc. It still never worked! Is there a possibility that the PSU isn't big enough to supoort 16gb!?

However that is a side issue compared with the pain I've had recently. In the past even with the mem issue (above) all has run extremely smoothly; high fps; high/ultra detail no probs...

but for a while now I experience minor to severe lag in all games / autodesk and even some windows applications. I have consistently checked all drivers, reinstalled windows, followed threads and tips; reset everything to default and vice versa, re-installed software, cleaned up drives, verified files etc.etc. but to no avail! Im on the verge of giving up and building a new system...

Has anyone got any wise advice on any of the above?

would be much appreciated cheers!