Windows 7 - Dual monitor: how to change the refresh rate?

Hi,

I want to connect a second monitor to my tablet PC. I succeeded once when I connected an analogue monitor (Samsung 1600x1200@85Hz). Now I want to connect a digital monitor (Samsung 1920x1200@60Hz) and I am having serious problems.

Typically both screens go black when I connect the VGA cable. The PC has dvi output but I can't find a cable since the connector on the tablet side is non standard.

I believe the root of the problem is that the monitor refresh rate is set to 85Hz in Windows7 and Windows7 does not allow me to set it to 60Hz.

My question is how I can change the refresh rate of the monitor?

Please look at the next 2 screenshots.

Try turning the tablet completely off, not sleep/suspend, then back on.

I did that and I thought the problem was solved, but as soon as I change the "display scheme" (mirror display, tablet only, etc.) I loose both displays.

The reason why I believe this problem has to do with Windows is that the first time ever I connected that Samsung monitor I saw on the display that Windows was "learning" of the different monitor geometries. It did that only once. So every time I plugin that monitor Windows7 believes it knows about it. But obviously it confuses the data of different monitors since it assumes it is 85Hz while it does only 60 Hz.

I have no problem connecting to a 720p HDTV with the SVGA cable. Windows7 chooses automatically the 1360x768 resolution and recognizes the TV as a Sharp. And I can cycle through all modes without loosing the displays.

The natural resolution of the Samsung is 1920x1200 which is outside the range of SVGA (I believe). However, the Samsung can simulate other resolutions. It does it when I first connect after turning on the tablet the first time. I can even boot in mirror mode (in the bios). Why can't I change to "monitor only" display scheme after that is a mystery.

Actually LCD monitors do not have a refresh rate. IFAIK it can be set to any number, 60, 75, 85, whatever and it really doesn't matter.
60 is used just because it is a lowest and a round number.

How about turn the unit completely off and back on with the external monitor connected.

Thank's for the suggestion. I did that before and I tried it again to be sure. What happens is that dual displays works great (mirror mode) during the boot up to the point where Windows shows its logo. But I loose both displays as soon Windows7 takes control.

So I needed to disconnect the monitor to get back the tablet display. A this point I need to add that I use a Motion LE1700 and Motion provides a utility called "Motion Dashboard" that has a convenient control to select between the five multiple monitor modes. I used that before. Maybe the problem is that "Motion Dashboard" was designed for Vista.

This time I just used Control Panel / Display / Change Display Settings and it started working when I selected " Monitor only". Now I can cycle through all display modes.

And I can run the monitor at full 1920x1200 resolution with the VGA connection.

It looks like a solved problem ... until the next time I restart the computer...

Thank you all.