ok, I read that the readyboot one is harmless and is because I disabled superfetch and prefetch. however, I cant get the computer browser one to stop..... I think that Is wagt causing my problems...
Superfetch and prefetch are best left switched on. In fact Seven doesn't actually need any real "tweaking" unlike previous MS OS'es. Aside from adjusting those and your pagefile, are there any other changes you've made?
From your event viewer screenshots there doesn't appear to be anything worth worrying about. None that would be the cause of this anyway.
If it was the graphics driver, you'd see:
"Display driver nvlddmkm stopped responding and has successfully recovered."
However since there doesn't appear to be any of those events, it's probably not the cause. (although the symptoms are similar.)
You mentioned this issue also occurred with your previous GPU, what was it? And what's the oldest driver version you've tried? Nvidias been putting out some crappy ones for a while. Maybe going back as far 320.18 or 320.49 might be worth trying if you haven't already.
Have you checked your hard drives health? It might be worthwhile using an app like
this to give it a check. With a quirky issue like this it doesn't hurt to check all angles.
When you ran memtest, how many passes did you let it do? Just the one or several? If there is something wrong with your RAM, it might not show up straight away.
What change did you make to improve your other games? Although if BF3 is still playing up, the issue may not be resolved. As for the choppy youtube playback, was it just in one browser or were other browsers affected as well?