I have just recently built a new computer and am trying to use my older vga monitor with it. The monitor displayed fine while installing the os but after it finished the monitor goes right into sleep mode. I updated all my drivers for the onboard video and my video card and have switched between the two in my bios trying to make it work. So far the monitor displays up to the loading windows screen then goes straight into sleep mode. The most annoying thing is that the monitor works fine as a secondary monitor, just not a primary. Any ideas? The monitor is also plug and play.
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Try loading W7 up in safe mode and set a safe video display say, 800x600 and then restart.
Could be that the video card is setting itself up for optimum resolution and your old VGA can't handle it.
What resolution are you trying to use? I don't think VGA can drive much beyond 1650x1050 or so...
if its an old vga monitor then 640x480 is going to be the limit, safemode is gonna be the only way of setting the display output to vga.