What you described in the title is a CPU . . .
There will be a chipset on the MoBo that is the graphics chip and that's the driver to look for.
Basically, we need more information about your motherboard. Any numbers or letter/number combinations on it? How about a name on the MoBo? Did the system have a brand originally, like Dell or HP? If so, was there a model number for the system?
Harder