After reading another string I should add that I have turned off the onboard video in the Bios.
Hi All,
I just installed a Nvidia 5600FX card into my K7N420 Pro motherboard (nVIDIA nForce 420D Chipset) and get spontaneous monitor shutdowns (eg the 19" NEC Multisync 95 monitor goes into 'standby mode' LED goes from green to orange). There does not seem to be any pattern to these episodes, sometimes it happens imediately after I boot WIN XP PRO, othertimes I can play 5 minutes of Battlefield 1942 or another game before it happens, and sometimes I can use windows for over an hour. When the monitor shuts down the computer does not respond (eg to Ctrl-alt-del and the HDD does not respond to pushing the windows button although sometimes the game music will continue). Occasionally the computer will reboot. Up till now I have been using onboard video with no problems.
I have tried reinstalling Windows XP PRO, updating all relevant drivers (i.e. Motherboard chipset, Video Card, Monitor) to no avail. I have 3 256 DDR RAM sticks in the DIMMS, 385 WATT power supply. The card has also run ok in other machines.
Your help is apprechiated.
Chris

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic