I did not look up the specifications on your Dell. But, I presume that it came with on-board video and you installed the GeForce card yourself.
The video drivers do not load until Windows loads. What is happening, is that the BIOS and boot screens are using the on-board video. You should be able to prove this by moving the monitor cable to the on-board connection.
What you need to do, is verify the settings for your Dell to use a plug-in video card in place of the on-board video.
You may need to disable the on-board video in BIOS settings. Or, you may need to change the setting for initial or first video device.
That said, it is also possible that you cannot disable the on-board video completely and will need to switch the monitor connection anytime you need to see the BIOS or boot screens.
Chas