Monitor not detected

I'm running into this and issue and I can't peg down a cause. I recently updated my Vista HTPC to Windows 7. When booting up I can get into the OS, but the screen goes black shortly after.

I have tried two monitors: the Panasonic plasma just goes black and when I try Samsung Syncmaster LCD it looks like it's searching for digital, then analog sources.

I have an Nvidia 8400 GS card and I've tried both the 191.07 and 195.62 drivers. I've also let Windows install the drivers after uninstalling the Display Adapter in Device Manager in Safe Mode.

When I start in Safe Mode I cannot recreate the issue. I tried uninstalling/reinstalling the drivers in Safe Mode.

Thanks in advance for any advice you can give.

you may need to disable the onboard video card in bios.also could be refresh rate.

Install the monitor driver and see how it goes.

Thanks for the info. I just tried installing the Samsung LCD drivers. I couldn't install them in Safe Mode. I installed Digital version of the drivers since I'm using DVI. It still "crashed". I also tried the Analog driver.

I also do not have on-board video, so I cannot disable that.

When the issue occurs the only thing I can do is do a hard power down. Turning the monitor off and on or reconnecting the DVI doesn't make a difference.

Use the device manager to install in safe mode.

I entered safe mode and uninstalled the driver for the Nvidia card. I tried to install the driver in Device Manager, but kept getting a message that it couldn't find the file.

So I rebooted into regular mode and installed the driver. It seemed to work for 5 minutes, but the issue occurred again.

Another thing that I noticed is that it may not just be the monitor/video signal. I am using ICS to share the network connection from this PC to my XBox 360. In the brief times it works I can get into XBox Live. When the issue occurs I can no longer connect to the network from the XBox.

I also noticed that when I connect this same LCD monitor to my WinXP box it give me refresh rate options up to 75 Hz. When I connect to the Win7 HTPC I only have the options of 59 and 60 Hz.

Any other thoughts?

Any other thoughts on this? It's a HP Pavilion s3321p Slimline PC. I checked for any Windows 7 drivers, but they only have Vista listed. I tried the Vista BIOS update, but it would not install.

i've been searching google about this and it seems that the threads i am coming across in differing forums are for hp computers (laptops and desktops) that are running the nvidia 8400 .can't be coincedence i shall keep looking to see if there is a fix.should have added that the notebooks are using external montors.