It's a GTX 780 that's been in there two years and never given me any trouble (except for when it misjudges where my screen starts and ends, which is fixed by reboot/unplug HDMI and eventually disappeared completely), never overheated etc. This issue appeared round about Windows 10 1511, where there's a green line flash across my screen (usually coming out of a game). It's minor and only there for a second at best, but it didn't happen at all before