BSOD Randomly Strikes When Gaming, "ntoskrnl.exe"?

Unfortunately sometimes it does not actually BSOD so no dump is recorded, however by luck i saved one to documents a few days ago and i put that in a folder entitled "olddump". After interrogating that one and the two that followed (unfortunately those ones are lost) i believe the error has something to do with ntoskrnl.exe something about symbols not found,I first started getting errors whilst playing battlefield 3, i can usually play bf3 reasonably with no lag, get the odd crash but these ones were different and ended up in a restart or bsod, the problem is and why i am so sketchy is the errors occurred extremely randomly, and sometimes after extended periods of gametime.It wasnt too much of an issue and i didnt give it much thought until i tried to play the guild wars 2 beta weekend, then i was hit with almost constant BSOD 1 or 2 minutes into getting in, this one was alot easier to pinpoint and after a few restarts i worked out it was FRAPS that was causing the problems, i disabled and it worked fine.In between this i was playing Age of Empires 3 on-line with no problems at all.When the BWE3 finished i gave my computer a spring clean, clearing out all dust, getting rid of all the "crap" i didnt need, removed all my old fraps videos and gave it a defrag, disk cleanup, full virus scan, i defiantly noticed the difference.I began playing Empire Total War and i received a number of BSOD, also some crashes which froze my computer and what i can only describe as gave a "blind" effect on the screen, the sound turned into a "hum"?I had a previous problem like this with my RAM so i did a memtest, it detected no errors at all. I have 1 stick of DDR3 RAM 4GB which i am unable to change at present.Last night i did every scan i possibly could, i ran a chkdsk, defrag, sfc scan, full virus scan, registry clean.. yet when i get back into Empire Total War this afternoon exactly the same thing although this time it just shut down.I have been monitoring temperatures at idle for the past week now and the temps rarely go above 42 idle and are quite consistent (GPU stays under 40), as i say fans are cleared of dust and can confirm they are all spinning.I think it is graphical related simply because it only happens when i play video games although the "ntoskrnl.exe" i got from the dump file makes me think it may be some NT coding, i am really not sure?Over the period of the errors i have done the following;

- updated my graphic card to the latest drivers

- carried out various scans/cleanups

- searched google to try and find what is wrong with limited success

- i have even tried gently shaking my desk incase something was loose or faulty

- removed/put back different USB (printer etc.) to see if that made a difference

I did notice whilst playing movies from DVD, it would freeze at specific points, no big deal but it froze my whole computer for a good 5 minutes when i tried to move on, maybe related maybe not.Things i am unable to do

- Buy/change hardware , unfortunately this is not possible at present although i am looking at purchasing more RAM.

Things i am unwilling to do

- Windows reinstall, i really would like to keep this as a last last resort, simply because the amount i would have to backup, i really dont have the time or patience although if it is the only option then i will obviously consider it.

Things i am going to try

- another ckhdsk, i did one but not sure i did it correctly, i tried to do one while posting this but had to exit it due to lagging my pc

- paying different games to really isolate the issue

- get another BSOD so i can grab the newest minidump

Specs (also in .zip file)
AMD Phenom(tm) II X4 B40 Processor
DDR3 4GB RAM
AMD Radeon HD 6700 Series