Benny, I don't know what your computer skills are.
But have you even opened your PC?
Instead of risking wasting your money and/or time - you need to diagnose a prolem, Isolet the problematic component, and then you will 100% know what to do (either replace, or reinstall..)
You said that your computers goes to BSOD only when it's performing cpu/gpu intensive task , right?
To clarify this, answer this question:
Does your computer goes to BSOD, when you jut live it open, and do notheing? or use office and internet (but no games)?
If it doesn't but but does only in games and testing - Than it's crearly overheating problem.
To diagnose this problem:
run your games, untill you see BSOD, than quickly open the computer, and touch with your finger CPU/RAM/VIDEO heatsinks.
NOw I won't get into complicated temperature calculations,etc.
The basic golden rule in electronics - is that you MUST BE ABLE TO TOUCH AND KEEP [/b] your finger on any part for at lest 10 seconds. If you can't keep your finger , or can't even touch something - IT IS OVERHEATING [/B]