Configuring dual monitors with nVidia in Ubuntu 10.04

I recently upgraded my notebook from 8.04 to 10.04 and have some issues regarding this upgrade. My notebook is a Compaq Presario 700 & it ran 8.04 without any problems. I upgraded to 10.04 using the upgrade feature after 10.04.1 was available.

I am unable to configure the nVidia driver & get an error message when the notebook is connected to the external monitor. When the notebook is not connected to an external monitor, there is no warning and the screen resolution is OK but when connected to my external monitor I get a warning message. Yet the external monitor seems to work fine even with the warning. Why am I getting a warning & what can I do to properly configure the nVidia driver to recognize my external monitor without an error message?