Does your Dell Latitude D620 have the Mobile Intel 945GM Express or the Mobile Intel 945PM Express chipset?
If you have the Mobile Intel 945GM Express chipset then you have the Intel Integrated Graphics processor. If the Intel IGP is defective then the motherboard would need to be replaced since the chipset is soldered to the motherboard.
If you have the Mobile Intel 945PM Express chipset then you would have the NVidia Quadro NVS110M discrete video controller. If the NVidia Quadro NVS110M is defective it should be replaceable.