Using 1.7v RAM on i5 750 instead of 165v

Your memory should run okay with that voltage, but you are significantly shortening the lifespan of your ram. As far as overclocking goes, you don't need the voltage that high unless you plan to run it well above 1600mhz. The memory frequency is set at a cartain ratio to your Bclk so when you increase the Bclk you are increasing the frequency of your ram. Drop that ratio (your memory multiplier) before you overclock your cpu so your memory stays in spec or close to it, otherwise you will hit a wall very fast. What you want to do is overclock your cpu to where you want it. Then download memtest 86+ and burn the iso to a disk. http://www.memtest.org/#downiso Boot from the disk and run memtest for a couple of hours maybe while you sleep, and if it doesn't fail it is stable. Drop the dram voltage and run it again until you run into stability problems, then bump it up a little. One more thing, there shouldn't be more than a 0.5V difference between your cpu vtt voltage and your dram voltage. I don't know why but I know that running it with more of a difference than that can damage your components.