My mothers system keeps freezing at exactly 1 hour and 20 mins. Nothing works (mouse,keyboard etc.). Have to press reset button each time to get system working again and after another 1 hour and 20 mins. it freezes once again. She had just recently upgraded her ram (edo) and had it reformatted. Also had a new fan installed. Have checked the power management and can not see anything that would cause it to hang up. Any ideas would be much appreciated. Thanks.

Not a solution but a workaround is to restart it every hour or so.

You may have some unknown lurking in the background responsible for the freezes. Go to the following website: http://home.earthlink.net/~rmbox/Reticulated/Toys.html and download,unzip and run the StartupLog program, and copy/paste the entire contents back here in this post. Also, are the latest drivers for the video card installed? To find out what your current driver installation is, Go to Start>Run, and enter: dxdiag. Click on the Display tab, and see if any problems are identified there. Another option is to try reducing hardware acceleration a notch by right clicking Desktop, choose Properties>Settings>Advanced button>Performance tab>Graphics>Hardware Acceleration. In Display Properties>Settings, how high are the color depth and resolution set? If the color depth is higher than 16bit true color, I'd try reducing that.

Make sure nothing is scheduled in your computer maintenance scheduler.(Task Scheduler) this normally has an icon in the lower right corner of the screen. Just a thought Jeck