I've experienced shut downs in Windows for around 6 months, albeit for the last month I've used GNU/Linux and haven't had anything similar to this problem. Any time my computer is running Windows (tested Vista, 7, 8.1) and I'm running a game (full screen or windowed, borderless, OpenGL or DirectX) my system will shutdown. My CPU fans are at max all the time (I can't hear the fans in my case but I run them max anyway, CPU fans are stock from the Corsair H80i pump, the pump works) and ditto my GPU. My CPU doesn't heat up paste 45 degrees or so (monitored by coretemp) and my GPU with fan speed max never peaks 45 degrees either. I haven't overclocked the GPU and I'm currently running at only 3.4GHz on my FX-9370 but it doesn't seem to affect the system, and running stock clocks or 4.6GHz (no turbo) in Linux doesn't show any abnormal temperatures either. I'm currently using a stock Vista install with mostly basic components installed but it still shuts down.
Omega 15.03 Catalyst drivers (patched for Vista, last native Vista driver would not install)
Vista Ultimate x64 SP2 (also tested in Windows 7 Ultimate x64 SP1, Windows 8.1 Enterprise x64, same results)
FX-9370 (3.4GHz)
Crosshair V Formula-Z
R9 270X (ASUS 2GB Direct CU II TOP)
8GB (2x4GB) Kingston Hyperex RAM, 4GB (2x2GB) AMD Radeon RAM
Coolmax 1000w power supply (less than 6 months old, aware they aren't OEM but it's worked just as well as my Antec did)
Kingston Hyperex SSD (SH103S3120G)
3 hard drives with partitions accessible to windows (NTFS), 1 WD Green 1TB SATA 2, 1 WD Black 2TB SATA 3, 1 SG Momentus 500GB SATA 3. There are various BTRFS partitions on those and another drive dedicated to BTRFS and a swap partition, which is a WD Caviar Blue 320GB SATA 2.
H80i with stock fans running max speeds (~2200 RMP), the 270x runs at ~3000 RPM maxed as well.
Omega 15.03 Catalyst drivers (patched for Vista, last native Vista driver would not install)
Vista Ultimate x64 SP2 (also tested in Windows 7 Ultimate x64 SP1, Windows 8.1 Enterprise x64, same results)
FX-9370 (3.4GHz)
Crosshair V Formula-Z
R9 270X (ASUS 2GB Direct CU II TOP)
8GB (2x4GB) Kingston Hyperex RAM, 4GB (2x2GB) AMD Radeon RAM
Coolmax 1000w power supply (less than 6 months old, aware they aren't OEM but it's worked just as well as my Antec did)
Kingston Hyperex SSD (SH103S3120G)
3 hard drives with partitions accessible to windows (NTFS), 1 WD Green 1TB SATA 2, 1 WD Black 2TB SATA 3, 1 SG Momentus 500GB SATA 3. There are various BTRFS partitions on those and another drive dedicated to BTRFS and a swap partition, which is a WD Caviar Blue 320GB SATA 2.
H80i with stock fans running max speeds (~2200 RMP), the 270x runs at ~3000 RPM maxed as well.