I will start with posting my pc specs , as explaining what the problem exactly is may take a bit more time.
ATI Radeon HD 4870 512mb
SB Recon 3D
HDD SamsungHD502HI 500gb -ish
monitor LG L1900R
Modecom 500W PSU
I am currently running windows 7
As to what my problem is, here goes :
While playing games suddenly the screen either goes completely black, white with whitish sqares, or black with blackish stripes, or very dark blue with a bit darker stripes and at the same time sound glitches a little and the pc freezes and i have to restart it. thats the thing that is happening most of the time. No BSODs, no errors, nothing. From time to time i get a monitor "error" saying "digital out of range - and some Khz's here ( not always the same )" There are some exceptions. for example when i play DOTA2 pc crashes just sometimes , mostly the game kinda minimalizes to desktop and i can still see the game cursor, hear the game sounds, and even use the skills in-game, however i can only see the desktop ( icons and all ) from there i can get to task manager and close dota, after which im getting "display driver stopped responding successfully recovered" . thats when i play DOTA2 and DOTA2 only. this never happend in any other game. However yesterday for the first time when playing WoW i got the black screen and sound glitch for a couple of seconds but after that the game continued for couple of minutes, next the black stripes happend after which the continued again and finally i got blue stripes after which PC crashed. i tried running the games in lowest settings possible and the time after it crashes is irrelevant to the video settings ( just yesterday morning WoW on lowest settings crashed after 30seconds, and the same day but in the evening on ultra settings i played for about 3 hrs before it crashed).
So those are the problems i am having. now i ll try to list the things ive already tried.
-formatted HDD ( and changed OS from win8 to win7 - which solved the problem for couple days )
-updated all the drivers
-installed older version of GPU and sound card drivers
-lowered GPU clock settings (using amd overdrive)
-overclocked GPU a bit
-checked all the temperatures ( with speedfan, everest, and vision engine control panel and also my hands and fingers during and before crash) and they were all normal
-changed thermal paste on GPU and CPU
-rested BIOS to default settings
-cleaned everything from any dust ( i do this regularly )
-tried running with another gpu ( geforce 6800gt - it worked, but the PSU started making weird noises so i took it out :S )
-tried unplugging everything i could that wasnt 100% needed ( two new pieces of ram - 2x4gb) and sound card
i think that would be all.
just some other things i can think of are recent changes to my pc. i bought 2x4gb ram ( exactly the same as the other 4gb just more ). bought Sound blaster sound card ( had some integrated one which i turned off in BIOS )and thats pretty much it.
I honestly have no idea what the problem is.
also i think i have to add that other than new RAM and sound card, GPU cooling system, the whole PC is almost 4 years old.
I would greatly appreciate any help and ideas.