When i turn on my pc, the screen blocks and some squares and lines appear on the screen. This started happening after overclocking my gtx 1070 strix. I contacted some stores and they say that it might need a reflow. Is there some way of fixing this without a reflow?
Dial back your overclock. You have pushed the card too far at the current voltage settings or you have pushed the card too far in general. If the problem doesn't resolve itself, try reinstalling the driver and or BIOS of the card to get it back to factory default. If it doesn't work still, then you probably screwed up your GPU.