have a dell latitude e6420 with 2nd gen i5 and without discrete graphics,can i install mxm card since option available on other series of same type.they come with nvidia graphics
I don't think the nvs 4200m is a mxm card. It will be soldered to the mobo (probably)
See the picture in the service manual at this link:
That is the GPU there under the heatsink in picture 4 and 5. It is soldered on.
You cannot upgrade the GPU on that laptop.