Hi, I've looked through a few threads on these boards and you guys seem to know what you're talking about. I've been having some fairly bad problems with my PC for a while now, random BSODs, usually with IRQL_not_less_or_equal, but had a couple of bad_pool_callers and a few other errors. So I've since done a full format of my OS drive, and installed Vista Business (I was previously on XP). However I'm still getting these BSODs, leads me to believe its a hardware error. Since my latest install, I've had two BSODs, attached the dump files to this post. From what I've been able to work out, they're kernal mode trap errors, but this doesn't really help me much in dealing with it. On a possibly unrelated (but probably related) note, whenever I try and use the computer for a demanding task, usually games, it hangs within 5 minutes of running. For example within 5 seconds of reaching the title screen on halo, and within 5 minutes of joining a server on TMN. These are literal hangs though, so unfortunately no BSOD messages or dumps . My suspicion is that one of my RAM sticks is dodgy, I have 4 512MB sticks and they're not particularly well matched (all the same speed size etc but different manufacturers, ages, etc). Here's my system specs: MSI K8N motherboard (nVidia nForce4 chipset) AMD 3200+ s939 (Venice core), 2 GHz 2 gig DDR RAM (4 sticks of 512 MB) BFG 7900 GS OC Graphics Card Thanks in advance for any help you can offer. As I say, I've looked round and found a few things but none exactly matching my circumstances. Thanks!