dual monitor problem (primary monitor disappears)

I've searched some forums and while i have found all sorts of dual monitor problems i haven't found this one.

I have a MSI M670 laptop ( with nvidia 6100Go graphics card ) and a Samsung SyncMaster T240HD. I always connected my monitor with a VGA cable on my windows xp and everything worked fine.
After i've installed Windows 7 when i connect the monitor to my laptop automatically the laptop monitor is disabled and the Samsung becomes the primary display.
If i press windows_key+P Computer Only is selected and whatever i select from the list ( duplicate, extend, projector only ) nothing happens and Computer Only is always selected.

In the Nvidia panel under the "Set up multiple displays" option after i connect the Samsung it becomes the only option so i cannot revert to my laptop display whatever i do.
Rigurous Display Detection does not help at all.

Any ideas ?

Have you been to multiple displays option in nvidia control panel and selected them both?

i cannot do that because when i connect the second monitor, the first one disappears from the list and only the second one is present.