The is the image of a computer with both integrated and discrete graphics installed. The on-board graphics are embedded with the motherboard. If you did not install the 630GT, you would have to connect your monitor to the on-board ports of the motherboard, as represented by either points "F" or "G" in the images above.
The installation of the graphics card would give you several extra ports on the rear of the system as represented by point "M" in the image above. With the graphics card installed, you should connect your monitor to either point "N" or "O".
Now, in Control Panel under Device Manager, you should see an image similar to the one below:
With your monitor connected to your 630GT graphics card, you should see something similar to this image. However, instead of it saying NVidia Geforce FX 5200, it should say something like NVidia Geforce 630GT
If it does not say this (or something similar) and your monitor is connected to your graphics card, that tells me the drivers for the card were not installed correctly. Since you say this system and the card are both Dell products, you should be able to download and install drivers directly from Dell.
If you
go here and click on the Detect My Product button, it should tell you exactly what drivers you need to install.
If you need further help we're here, but we'll need as much information/images as you can get to us.
-Wolf sends