How to fix an "overlap" or collision between multiple monitors?

Question

When I connect my Samsung SyncMaster SA300 to my laptop running Windows 7 64 bit, I get a weird behavior.

When the lid is closed, everything seems to work:

When the lid is open, there is a weird collision between the monitors. Only one monitor is identified, and it seems to be a "merge" of the two monitors.

I installed the latest drivers from Samsung's site and ran Windows update. What is causing this, and how to fix?

Update - now the screen is dark with a "check signal cable" box. The cable is connected, and nothing I do (reinstalling driver and playing with monitor's internal config didn't seem to fix it).

Solution

Clicking Windows-P and extending the desktop to the other monitor helped with the 'check signal cable'. I always forget to try this (even though it was right there in the Screen Resolution settings!).

Comments

[ripper234]

Please see the answer I posted - the problem is solved now.