Windows 7: my monitor is no longer recognized, screen resolution is decreased

I installed Windows 7 Ultimate 64bit SP1 on my replacement boot disk (old one died) on May 25/12. Since June 4 (and at least once before that), daily my monitor is no longer recognized and the screen resolution is decreased. It doesn't know about my Samsung monitor anymore.

It now shows this:
Display: Generic Non-PnP Monitor, Resolution: 1024x768.

When I run personalize, screen resolution, detect,
Windows sees the correct monitor (SyncMaster 245B(Analog)) and sets the resolution to 1920 x 1200. Meanwhile all my open apps are resized smaller, I have to resize them again.

I'm not sure what the cause of the problem is. It's not necessarily happening at the same time and I can't seem to find an error in event viewer. Any ideas how to troubleshoot and resolve this issue?


Latest drivers for PC hardware I installed - video and monitor:

-video card drivers
from guru3d.com, latest video drivers, try:
Nvidia GeForce 301.42 WHQL WinVista 7 64bit
Ver 301.42 WHQL, May 23/12,161MB

-monitor
Samsung-Display-SyncMaster 245B/245BW/245BPlus(Analog) 13KB, 20070410082319062_SM245B.exe
It's dated Nov 2007, so didn't install the Microsoft Windows Update one, Installed 20070410082319062_SM245B.exe from Samsung.

Hardware
1) Video card-Zotac 9600GT amp 512 PCEI
2) Monitor: Samsung SyncMaster 245BW - 24", Resolution: 1920x1200

The most interesting part of your post for me was 'Since June 4'.

I have also been having display problems recently. In my case one monitor would have a display only on bootup then go black, another monitor would always be black and Change display settings would say that there was no monitor.

When I tried to do a System Restore it said that there had been a Windows 7 Update on Jun 4!

I was able to get the two monitors eventually to work as they once did, not using Change display settings but rather by using Catalyst Control Center which on my computer is the factory installed video adaptor interface.

Finally, I didn't understand 'When I run personalize, screen resolution, detect, ', please explain.

Start, control panel, personalization, display, adjust resolution, click detect
or
right-click in the desktop, screen resolution, click detect

My last windows update was June 3, for MS Office 2007. I didn't do any windows updates for the video card or display. June 4 was the second or third time it happened, so I started to track it more closely. It seems to be happening daily sometime between 10am-3pm, not sure. I disabled adobe flash updates today, which runs at 720pm, repeats every hour and last ran at 120pm since the issue re-occurred today between 1-2pm.

First, check if your VGA port OR cable is working correctly. If possible, connect your screen to a different display port on your card.

If this doesn't fix it - completely remove the Nvidia drivers, reboot, reinstall and then reboot again. (Seems simple, but often does the trick)

Thanks for the reply. The problem happened again June 12, early in the morning, so I un-installed the NVIDIA graphics driver, reboot, re-installed the NVIDIA graphics driver, reboot.

The problem happened again June 13, around 24 hours later, so I moved the VGA cable to the second video port. I think the video cable is ok.

I wonder if the video card is overheating because I have the new boot disk on the bottom of the case
and the original boot disk still running behind the big fans. When I get a chance, I was going to move the new boot disk where the old one is (but I need to unscrew the big fan to get to them first) and put the old one on the bottom but not powered on unless I need to get more files off it. My hard disks are already set in power mgmt to turn off if inactive for more than 20 minutes.

I finally found the time to move the hard disk to it's permanent position in the hard disk rack behind the big cooling fan. Since then, the problem hasn't re-occurred, confirming that the video card was overheating as suspected.