In last years I was playing mostly soccer manager games( Fifa Manager,Football Manager and manager mode in Pro Evolution Soccer), all of them have 3d match engine. My system appearently had no problem running them. About 3 years ago,my Pc started to have horizontal lines on the screen, bluescreens and then problems got alot worse in a week and my pc became unusable. Then thinking that my graphics card( Sapphire Ati/Amd HD3870) was about to die, I bought a new graphics card, Zotac Geforce GTX 970.I installed it into my Pc case, then uninstalled the Ati driver and tried to install Geforce drivers. I had alot of trouble while installing it, after many hours I found a way on internet to do it, I got something like Super-Admin rights and was able to install the driver. Everything was good, there was no bluescreen but one thing I noticed was, before Windows login screen, my monitor was sometimes going to "sleep mode" displaying a message on the screen(something like "entering sleep mode") and it was going blank and after about 6-8 seconds my monitor was coming back visually. Like I wrote before, I was mostly playing soccer manager games.But in the last weeks I started to play old(but with relatively high-quality graphics) games like Crysis,F.E.A.R, STALKER, Doom 3, Need For Speed Shift...There was almost no problem( other than the black screen before Windows login which I wrote above, it still happens sometimes and have sometimes horizontal lines on scrollbars, acutally this happens only on scrollbars though far from often) , until a few days ago... A few days ago, while playing Crysis, my system suddenly restarted.Then I played again and after a while, again the system restarted. I thought(and hoped) there was a problem with Crysis, Yesterday I decided to play COD2(Call of Duty 2) and after a while again system restarted. After restart I run GPU Temp app and my gpu was about 47C. After a few hours, I decided to run a "stress test" and downloaded and run Furmark and also simultaneously run Speedfan to measure temps of cpu and hdd too. In a few minutes, graphics card's temperature quickly got higher, it reached 85C and stayed there, at the same times cpu temperature was getting higher slowly. After about 11 minutes, my system restarted.At that time the graphics' card temperature was 87C and cpu core temperature was 57C. I don't think they are extreme values, are they? Today I repeated the same stress test, after 11 minutes system restarted again, like in my previous test yesterday. At that time graphics card temperature was 85C and cpu core temperature was 58C. I want to add that the aire conditioner in my room was running and the room was cool . What do you think about the temperature values I wrote above?If they are not extreme then I think that the problem may be an issue with my psu or graphics card.I may try reinstalling/updating the Nvidia driver but I am sure it will be difficult to install it like it was when I first installed it. Do you think my psu is enough for Zotac GTX 970? Some of my pc compenents are actually very old, about 9 years old. My current computer specs are: Zotac Nvidia GTX970 600W Coolermaster RP-600-PCAP Intel Core 2 Quad Q6600(2.4ghz) 2gb DDR2 OCZ Ram 3 internal hdds, 2 internal optical readers/burners Windows 7 32bit OS I am thinking about buying a new psu but I would like to be sure that it is a problem with the psu not the graphics card or other thing.Also, I want to add that I don't do any overclock on my system.