I finished putting together a new build (component list here) yesterday, and everything has been going smoothly until a short while ago. I'd finished several hours of Prime95 without incident (just to cure the thermal paste as recommended by some folks here) when Windows Update (running Win7 Pro 64-bit) found a new driver for my ASUS VW223B monitor, which I allowed to be installed. Afterwards, I noticed that the mouse tended to disappear off the right side of the screen as though there was more space there and checked out the Screen Resolution menu. Sure enough, the monitor was being shown twice, as a generic monitor and as the VW223B, together in a dual monitor configuration. I changed the settings to only display on the VW223B, which dealt with the issue. Then I opened the nVidia Settings menu to see if there was a relevant option there that might be better to use. I also had Speedfan and CPUID's HWMonitor running at the time. Upon clicking the "Set Up Multiple Displays" option in nVidia Settings, the window locked up, followed by the entire system locking up with the monitor turning off and back on repeatedly. I used the case's power button (four-second hold) to force a power-down. Now, whenever I turn the system on, there is no video stream to the monitor, and the system spins up the hard drive, spins it down, and resets, doing the same thing over and over again. I've found, through a little experimentation, that connecting the monitor to the mobo's video outputs doesn't get a signal to the monitor, but having the monitor's data cable unplugged from the video card causes the system to continue booting. Connecting the monitor after the boot process is underway sees otherwise normal functioning. Opening nVidia Settings works fine (haven't tried reproducing the conditions of the initial lockup, though), and the card seems to be functioning normally aside from, it appears, failing POST whenever connected to a monitor. I'm thoroughly confused. The entire system is running at stock settings; no overclocking had been attempted yet. Any ideas, suggestions, or tests to run?
The answer to my question appears to be "No", at least in this case. Reinstalling Win7 changed absolutely nothing. If the monitor is plugged into one of the graphics card's ports, I get no output to the monitor and the computer seems to fail and retry POST endlessly. I can change the BIOS setting to use the onboard video output during POST and boot, which works perfectly fine so long as the monitor is connected there instead of to the card. I can also simply leave the monitor unplugged until the second time I see the disk access light on the case flash, which never happens when it is failing to boot, and then plug the monitor back in. That, however, is not a viable means of dealing with the problem in the long term.
I'm going to see if the problem persists with a different monitor since the problem first occurred after installing a new driver specific to my VW223B. Unfortunately, I don't have any other systems in the house with new enough graphics cards to test the monitor on them with meaningful results.
Well, now I'm even more confused. I tried booting the system with an old Dell monitor connected the graphics card, and it worked fine. Then I tried a second VW223B (since I'd bought a second one a few years ago for another family member), and it worked fine, too. Then I plugged the first VW223B back in, this time without the USB connection (the monitor also functions as a 1-to-3 port replicator); it worked. Then I plugged the USB cable back in (the configuration in which the problem first appeared), and it still worked. For whatever reason, the problem no longer seems to exist.