Hello all, I just built a new rig last week, and when I'm running benchmark for GPU, the computer hangs/freezes and a hard reset must be done. Sometime it hangs while watching a DVD, not even under extreme load. My computer specs are: Motherboard - Asrock z77 extreme9 CPU/Processor - Intel core i5 - 3570k 3.4 GHz (I didn't overclock, only ran stock speed). Memory - G.SKILL Ripjaws Z Series 32GB (4 x 8GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL10Q-32GBZL Video Card - ASUS ENGTX460 DC TOP/2DI/1GD5/V2 GeForce GTX 460. nVidia driver version is: 301.42 Operating System - windows 7 enterprise (64 bit) version 6.1 build 7600 (I didn't install any updates or service pack, although this happens with windows service pack 1 as well, I installed fresh copy of windows 4 times this last weekend... :-s ) Hard Drive - Kingston C300 128GB SSD (operating system is installed here), other Hitachi HDs for storage. PSU - Thermaltake Black Widow W0319RU 850W Bios version - 1.50 I connected the video card in PCIE 2 as recommended in the user manual (for single card). What I tried so far: Ran stress test to the CPU using OCCT 4.3.1 - finished successfully Ran stress test to the memory using OCCT 4.3.1 and MemTest - finished successfully. Ran stress test to the GPU using OCCT 4.3.1 - sometimes it finished with errors, sometimes it hangs in the middle and sometimes it finished successfully. Ran benchmark for GPU using Heaven DX11 Benchmark 3.0 it hangs in the middle. When I switched the video card to PCIE 1 the above tests all finished successfully. Yesterday I also tried to remove all the unnecessary devices and cables (no network, sound etc.), in the bios I returned to the default settings and tested with only 1 stick of memory and only the SSD connected. Again, the same results. I then tried with a different stick of memory in a different slot, and still I get the same freeze. I also tried with nVidia driver version 296.10 and with windows service pack 1. I'm not really sure what else can be done... Do you think there is a patch or a different driver version that I should be using in order to fix this? Maybe some configuration in the bios? Do you think that the motherboard itself could be defective? Thanks for your help!