random BSOD on Windows 7

need major help here from major geeks, last february i've been having random bsod's on my workstations (gaming cafe), ive tried erasing, cleaning, resitting, and blowing the dust away on my ram, vidcard, and board, i've also updated my windows 7 thru windows update and update my drivers, and still having same random bsod's, so a couple of weeks trying hard to resolve the issue i've decided to reformat my computers and installed windows 8.1 and much to my delight, BSOD is finally gone and my cafe is running smoothly, but a couple of weeks after that i ran into a problem, some of my customers are complaining about spiking and lag on games like Garena League of Legends and Garena HON, but having no issues on Dota 2, CrossFire, Dragon Nest, and other online games, so i've decided to switch back to windows 7, so i've reformatted my computers again and voila Windows 7 is back and so does the blue screen of death, ive scanned for bad sectors, viruses, malwares, and all have thesame results, everything is clean, ive also tried memtest and scandisk and still everything is ok, the past few days have been really frustrating for me, i've tried every cure i know for this issue including reapplying the thermal paste on my processors but still having the evil BSOD, hope u guys can help me with this, I've attached my recent minidumps from my computers,

my 5 year old computers specs are:

Intel DG41RQ
Intel Dual Core
2gb Kingston RAM
320 GB Seagate HDD
1 GB GT220 VGA