Well It still seems like there are two problems. First two of the four crashes were still caused by your video driver
. All four however were memory related. Since you replaced the video driver alreaady I think it would be prudent to start looking at the memory. I do have a question. Does it blue screen in safe mode )F8)?
Now onto the memory. you should go get memtestx86 and run it for 5 passes. It is going to take a lot of time. It will tell us if there is either a memory problem or maybe a heat problem.
Im not sure but if you havent run a system file check
type cmd in search>right click and run as admin>sfc /scannow
If the memory and the system show no errors we will get more aggressive. if we need to get more aggressive you will need a backup and a win 7 dvd.