BSOD had 5-6 different messages

Hello guys, where to begin well first off my first computer broke so i went out and replaced everything, apart from the processor. i was previously on windows 8 but downgraded to windows 7 ultimate 64bit, and since installing the new windows and parts i have had 5-10 blue screens a day while playing my games, sometimes i can play for about a hour without any blue screens sometimes 10 minuets i have had different errors stop codes and ect ect im not very computer smart i have tried googling the error's that pop up and many of them tell me to try to mem test my computer i have done this and it comes up with no errors im at my witts end after trying to fix this problem by myself, so here i am Begging someone to help me i understand its helpfull if i can post a dump file or what ever it is but i have no idea how to find it or post it hopefully, someone can assist me

i have already done the windows mem test does that not check for ram issues if not i'll have to get hold of a blank cd or usb will post results when i manage to get them thankyou for the help.