Hi Tony,
Thank you for replying with the status of the issue. Sorry to know that the issue is still not resolved, your efforts to resolve this issue are highly appreciated.
I suggest you to follow the method below and check if this helps:
Method 1: Perform a System Restore.
System Restore
http://windows.microsoft.com/en-US/windows7/products/features/system-restore
System Restore disclaimer: When you use System Restore to restore the computer to a previous state, programs and updates that you installed are removed.
Method 2: Uninstall all the hidden devices:
Step 1: Refer to the article below to enable the Hidden devices in device manager.
Viewing Hidden Devices
http://msdn.microsoft.com/en-us/library/windows/hardware/ff553955(v=vs.85).aspx
Step 2: After enabling the hidden devices, uninstall the devices from the device manager.
1. Press Start button.
- Type device manager in start search box.
- Select Device manager from the search result.
- Uninstall all the hardware which are grayed out also uninstall the display drivers completely.
- Restart the computer and install the display drivers from manufacturer's website.
Hope this information helps, please reply with the status of the issue for further assistance.
Hi Rizwan
Unfortunately I did not have an old enough restore point before the problem occurred. I did not find anything that looked relevant in hidden devices, but in normal device manager mode when I clicked on "Monitor" it opened an entry "Generic PnP" even when there was no additional monitor or projector attached. When an additional monitor was attached there were two such entries. I disabled them both and I have found I can now adjust the resolution of a second monitor to a different setting from the laptop screen.
Thanks for your help.
Tony