Hey Im posting here as im certain this is hardware and not a software issue. So i had an issue here, which i thought was gone....its not. I got a new HDD/PSU and GPU at the same time, i treated as a new install (so old HDD disconnected) installed windows etc and got up and running. The new PSU was 650W named unit. Connections inside comp are Mobo - 24pin (and the 4 pin CPU one) GPU - 2*4pins pcie power (MSI GTX 560 1GB Twin Fozr OC edition, i have not pushed any further OC on the GFX card) HDD 1TB - Sata HDD 250GB - IDE/Molex Optical Drive - IDE/Molex Now a few weeks onwards the Blue Screens are reappearing again. The MOBO sometimes comes up at boot stating that the "OC is causing instability" and goes to factory defaults, this happened on the old build and the Blue Screens stopped (cpu-z shows reduced voltage and CPU speed down 1Gig). When the MOBO does this I go back and reload the OC settings so have not tried with the OC off (as a bought OC build im not doing this). 1. Memtest was peformed on old build had no issues 2. Temps seemed fine on old build 3. It seemed that an insufficent PSU was the issue. So i have a few questions 1. PSU - Should this be sufficent to power the system including the new GFX? As far as i know it should be more than enough. 2. Is there a software to monitor temps that will survive a Blue Screen (i.e. its running then there is a blue screen i can check logs all way upto blue screen to check temp). 3. What else? I suspect the PSU again, as i have a powerful OC GFX now and the OC mobo if the PSU is again an issue? But from what i have heard the 650W should be sufficent. At last resort ill need to get in touch with the Company that i bough MOBO etc from, but if i have to send back etc thats gonna be a pain. Thanks p.s. Full system specs click on my sig below. p.p.s - From a post below - "Cheers for info, i think i should clarify a few things. This was a prebuilt OC'd rig (MOBO/RAM/CPU/COOLER) the company (aria.co.uk) apparently stress test for 24hrs to ensure its alright. I do have a years warranty on it. However im not supposed to touch the OC settings in bios. I just meant that someone sayin "scrap the OC and run stock" was not a viable option as i have paid for the OC. When the MOBO reset itself to stock speeds, there is the Aria settings saved to the CMOS which are loaded again. I only mention the memtest as someone on the original post i linked before suggested this, im not using that as overall system stability The Blue screens themselves are random messages, "PFN_LIST_CORRUPT" is one, problem with "win32k.sys" and a few others, the blue screens are up and system reboots again pretty quick to check. These are pretty random, in game, in windows, one time after it had been on sleep it blue screened 2 mins later."