I just switched to 2 - 24" Asus monitors. I had been running 2 - Samsung 20". With the Samsungs, one was fed by the DVI out of my vid card and the other utilized the VGA out. With the ASUS monitors, one is fed with the HDMI out and the other frim the DVI out with a cable that terminates at the monitor with an HDMI plug. Vid card has 1 each, HDMI, VGA and DVI.

Everything went without a hitch on the install. However, the primary monitor has a 1/2" black border all the way around. That's to say, the image (track view in SONAR) doesn't extend to the bezel. The other monitor (console view in SONAR) goes all the way to the bezel top, bottom, left and right sides.

Windows 7 64 bit - video card is an ATI Radeon 5400 series.

Resolution is set the same for both monitors. 

Any ideas?

I assume the one with the black border is connected to the DVI-D connection? The max resolution DVI-D supports is based on the number of pins supported and in the connector. But even at a lower resolution, there should be settings on the monitor itself to adjust the window height/width. I would try that first. If not, try swapping the connections to the monitors and see if the issue moves to the other monitor; if so, it may be a resolution issue with the graphics card and may be adjustable in the windows software for "Display settings." If it is not adjustable on the hardware and does not swap with cable swapping, it may be an issue with the monitor itself, and I would recommend contacting ASUS about it.

I had looked at some new monitors at Costco, including Samsung but they were all HDMI interface and I bypassed them.  One of the problems is PC audio.  If you use an HDMI connection, Windows automatically switches the default audio playback device to the HDMI.  If you want to use the PC audio/speakers you have to manually change the default playback device to "Speakers" (PC sound). 
 
 

Samsung monitors are very good in my opinion.

As for the HDMI audio stuff, that in installed by the graphics card driver, not the monitor; my Samsung monitor doesn't even have speakers but Windows/AMD Catalyst insists on installing HDMI audio. Easiest answer is to go into control panel/devices and disable (but not uninstall) any listed HDMI audio devices. That way you will never be troubled by them again.

Thanks for all the input folks. I'm not goiing to be back in the studio until tomorrow. But I will look at everything mentioned in the responses and report back!
 

Why not use the other connection, I use the D sub and the old blue thing what ever they are called and it works fine, When I tried the HDMI I had resolution issues and couldn't match my 2 monitors at all. 
All new cards , even on board have the 3 connections now. But HDMI seems better for a TV than a computer monitor. 

This is the Radeon driver setting. If not mistaken, it's something called the monitor 'scaling' setup. Set it to full or 100% and the dark border is gone.

You folks have given me a lot of great information!

Will report back as to what transpires. Thanks! 

Turns out it was in the Radeon settings. It was under 'Catalyst Control Center'. 'Underscan' was set to -15%. When I moved it to 0%' that took care of it. Thanks all!