Dell E6510 Dual Monitor Support

Hi All,

I need some advise/help on the following.

I have a Dell E6510 With Windows 7 Professional Loaded, and am experiencing the following issues.

1. When Connecting a secondary monitor 17" to the laptop the extended desktop feature works perfectly, with no issues. 
2. When Connecting a newer bigger monitor the Dell P2312H, and using the extended desktop, the bigger monitor "takes" over as the primary display and disables the laptop display completely. The only way around this is to unplug the Bigger Monitor. Both the display's run at a resolution of 1920X1080 and I cannot see this being the problem.

The following is what I have done to try and resolve the issue.

1. Replaced all the Cables, this being the power cable & the VGA Cable.
2. Updated the Bios to the latest version, updated from A07 to A011
3. Downloaded the latest Graphics Drivers from the Nvidia Website.
4. I have checked all the power settings, and can confirm that they are correct.
5. I have tested the monitor on another laptop, and have not had the problem for over 1 day.

Apart from this I am not sure what next to try.

Regards

Ryan