A lot of blue screens

Hi everybody,

First, I'm sorry for my bad english   and if I posted in a wrong place.

I searched on the forum for my problem, but every topic has a different program causing the blue screens, so I decided to post a new topic. I'm sorry if I did something wrong.
This is my PC:


This summer my video card has burnt (HD3870x2), so I bought another one plus another 4GB RAM (same model) and a HDD (WD10EARS). After I installed every component, I turned on the PC, but it couldn't accept 8GB RAM (even if the limit of the motherboard is 16GB). I removed the new memory cards and I turned it on again. It worked, everything was perfect. Next day... boom, a BSOD caused by dxgkrnl.sys. I had to restart the PC for many times. When I succeded, I thought the problem was the GPU's driver so I installed the newest one from the producer's site (AMD). It had no effect. I reinstalled the OS. For a few days there wasn't any problem, but when I installed a new game (I don't remember which one), it started again. Many, many blue screens. I decided to stop playing games for a time. I didn't have any problems for 2 weeks, but when I started to play again, the BSODs started to play with me too... I don't know why, but there weren't so many as before. Now, in the minidump folder I have almost 50 minidump files o.O
46 caused by dxgkrnl.sys (STOP: 0x00000116)
2 caused by win32k.sys (STOP: 0x0000003b)
1 caused by ntoskrnl.exe (STOP: 0x00000050)

I have some screenshots:





I'm full of it. Please, help me