Intermittent freezing problem

[ggreggs2427]

I have a user that is running Windows XPSP3 on a Dell Optiplex 755 and the user's PC keeps freezing and we have to do a hard shutdown. I have changed out every piece of hardware and did a clean install of the operating system, update the bios, updated the video driver and I am still having the problem. We have eliminated outlook 2007 as a problem and I've attached the log file from hijack this. I need some help on this one.