Details about my system first - AMD PhenomII x2 550 Black Edition 500gb HDD Western Digital 400w Corsair PSU 2GB OCZ DDR3 Memory (TESTED USING MEMTEST86+ PASSED WITH NO ERRORS) Gigabyte GA-MA785GMT-UD2H Motherboard with On-Board HD4200 I ran Linux Mint 7.0 Then Linux Ubuntu 9.10 Then Windows XP with Service Pack 2 Then Ubuntu 8.04 My system started crashing about a week after I built it. It started with a crash every few days, usually either in Firefox or when I had multiple apps open. It started crashing on startup too, before the boot menu after GRUB loads. [Linux] The crashes are in 2 different forms. Crashes when installing from CD or in the system - the screen freezes, keyboard and mouse unresponsive, screen has interference in the form of small blocks of horizontal bars, kind of like what you see on the output of a graphic equalizer or frequency bars on a fancy audio system. These are arranged in several columns on the screen. [XP and Linux] The crash after GRUB but before the boot menu is weirder, a few dozen clumps of characters, like ÉÉÉ (mainly them, including square boxes, normal characters, and characters from other languages) dancing over the screen, no pattern is perceivable, refreshing after every quarter second. The crashes became so frequent that the system was unusable. I thought that it might be a Linux driver issue, or maybe the system was trying to address memory locations which weren't there, or maybe it formatted the HDD incorrectly (I've heard of problems with Windows selecting too big a partition for 500gb HDD's which was causing disk formatiing to hang at 100%). Maybe it could even be a power fluctuation with the PSU playing up. One thing that I doubt is heat. The system has not gone anywhere near critical levels, the bios reports stable temps rarely above 45-50 degrees (when it was usable). Usually (about 95% of the time) it hovers around 40 for the processor. After several install attempts, and re-formats with GParted and live CD's, the system does not successfully install any OS from a CD without crashing. This crash happens before you even get to formatting the disk. Or it crashes when formatting. Or it crashes when loading the files. Complete waste of space! So. Before I start sending things back to manufacturers, I have one simple question. With the above description, which component is the likely culprit and why???