Random crashes (BSOD and freezing), multiple drivers responsable

Computer crashes to BSOD (or just freezes) while playing games, browesing and even idleing.
It started a week ago, at first was BSOD atikmdag.sys driver so i thought it was the new ati drivers update i installed. Tried changeing drivers to nearly every version and it still crashed.
Reinstalled Win 7 and it wouldnt boot after the install becouse i had devices plugged in the computer-back usb hub wich worked fine till now. So after i unplug everithing from the usb hub i manage to boot windows install all the programs and drivers . But nothing changes.
Hard disk scans, no errors.
Runned Memtest86 for something like an hour, no errors. Prime95 memTest gave errrors after 2 min. So i removed 2x512 ram sticks wich left me with one stick of 2 gb and run Prime95 again. Error after 25 min.
In the dump files i attached, there are some dump files with nvidia driver also, wich is becouse at one point i switched my graphics card to my old nvidia card bud it still gave BSOD.

Its been 4 days and i dont know what else to try, still didnt manage to isolate this problem (it can be anything). My Ati radeon 4670 still has warranty but im not sure the card is the problem here. Im kinda desperate, please help . Thx :)

Sorry, i was sure i attached the zip file... ill do it as soon as i get home.

Here are the dumps. Theres one more problem that maybe is connected.
It takes me 3 minutes to turn the computer on, when i press the button i hear the vent start spinning for half a second then stop, and i have to do this for a while untill it "catches" and stays on, but then it doesnt show nothing on screen so i have to restart and get it into this state untill finaly it beeps and starts booting.

Thanks for help

I have been running win 7 64 bit basicly since it was released, and it always ran smoothly. I will try what you suggested anyway . Thanks for your time .