There's a lot of information on your system at support.dell.com.
If I understand the specs correctly, you have an Intel 965PM chipset, without integrated graphics. (Another version uses the 965GM chipset, with integrated graphics, but that's not what you have.)
I doubt that it's practical to convert to the chispet with built-in graphics, but you could ask your repair shop. The performance of the nVidia graphics is probably much superior, but you appear to not benefit from that.