Are you set for Dualview in the nVidia Control Panel?

If not, your 21" might be receiving a signal that is out of its range. You fail to mention the resolution the secondary is set at.

Thanks for the quick reply! The DVI cable is the same one I was using with that monitor just a week ago, before I got my new system. But I suppose it could have gone bad during the switch. I didn't touch the monitor end of the cable, left it plugged in there, and only unscrewed/unplugged the computer end. I could check with Radio Shack to see if they have those...we don't have much for tech stores here.

oops sorry, missed the other reply!  The secondary monitor (21") is set to 1600 x 1200 in the screen properties.  I thought that the two monitor images on the screen resolution window meant that it was in dual monitor mode? Where do I look to confirm this?

I think it means that it detects two monitors, but when you click on each one you can set the resolution.  the second monitor is off unless you flag it as "attached."  Other than that, I'm not really sure what could be going on. =\ 

EDIT: I'm looking at the properties screen, not the driver window. 

Like I mentioned before, the nVidia Control Panel.

Since you are running that monitor at its max res, make sure the refresh rate is not set too high.

You can check the cable by switching them around. If you switch them and the same thing happens, it is not the cable. If your primary monitor goes blank, it is the cable. That is assuming that both cables are DVI at both ends, and you are not using an adapter.

I work in Walmart's Homeoffice IT and setting up dual monitors is a bit tricky. It is not likely your cable, most likely it is onboard video driver is still active in windows. Here's what I do to get dual monitors to work.

1. Download the latest drivers to the local hard drive. 2. Make sure the BIOS onboard video option is set to Auto or you might need to set it to Disabled. Try Auto first. 3. Install the card 4. Reboot the pc and hit F8 and select "VGA Mode" to boot into windows. 5. Install the Video Card drivers, do NOT reboot 6. Go to control panel in windows and Disable the onboard video do not uninstall the onboard drivers 7. Now reboot the pc.

When your pc has rebooted into windows your new video card drivers may automatically setup your monitors as Primary and the other Extended which is what most people want. Of course once configured you can make the necessary changes.

I'd be interested in your results.

Thanks Mark for the suggestions! I was searchng online for the specs of the 213T, came across that model (still for sale) through Amazon. There was a link to the pdf manual, so I opened it and read through it.

I *just* figured out the problem and fixed it! I opened the pdf manual for the monitor, which had a Troubleshoot table. First thing on the list was "No images on the screen.", the checklist for that included "Can you see "No Connection, Check Signal Cable" on the screen?" and one of the suggested solutions was "(Connected using the DVI cable)  If you still see an (error) message on the screen when the monitor is connected properly, check to see if the monitor status is set to analogue. Press Source button to have the monitor double-check the input signal source." So I turned on the secondary monitor (and got the floating check signal cable icon) and found the Source button and pressed it. Screen went blank for a couple seconds, then the image of my desktop came on! I was able to see my cursor on that screen and move windows from the primary screen over to it and back. yay!

Thanks so much everyone for helping to troubleshoot this thing! That's what I really love about this Wincustomize community...you all are the best!

I guess I can now confirm the saying:  RTFM!

Awesome!  And I'm glad you stepped in Mark, I was way out of my league.