I started having a problem with random yellow horizontal lines appearing for a split second on both of my monitors, being output from an EVGA geforce GTX 660 OC.
They are about an inch long and can appear anywhere on the screen.
The problem started clearly after I manually set the video card fan to 75% for about 5 seconds using Open Hardware Monitor. There were hundreds of artifacts per second all over the screen! I then turned the fan setting back to normal and it slowly revved down, but in the process, still artifacts heavily showed until it went down to normal speed (around 35% or 1020 RPM).
No overclocking or voltage mods were applied, just the fan speed from the program's window.
However, now, I am getting the random artifacts just when the computer is idle with chrome open and nothing else.
I have reinstalled nvidia drivers, restarted the computer, left it off overnight, and used the default Windows 8.1 drivers. No luck.
PC (built in 2013 July):
Core i7 4770k
Asus z87 mainboard
geforce gtx 660 EVGA
700w thermaltake psu
2 ssd and 1 hdd