Vostro 470, Multi Monitor

Hallo Community,

until yet I worked on my DELL Vostro 470 with two Monitors. Both Monitors are attached to an addtional graphic-card built in, in the system.

=> NVIDIA GeForce GT 610.
-> The first monitor ist attached via HDMI to the NVIDIA GeForce
-> The second monitor ist attached via VGA to the NVIDIA GeForce

Today I want to use a third monitor. I attached a third Monitor via VGA to the internal grahikcard.

But after the reboot of the system the third monitor keeps black.
After some researchwork I found that i have to activate the multimonitorsupport in the bios to activate the internal gaphik.
After doing that the VGA Monitor still keeps black after booting.

Having a look to the device manager (Win7 64 prof) i saw that there is no internal grahic-card listed
in the grahic-card-section. Only the NVIDIA (and a virtual card for VMWare) is shown.

Doing some additional researchwork in the www I found that a newer BIOS is avaiable. So I upgraded
the BIOS to latest Version "A14" from 2018.

But this doesn't solve the problem too.

Now I'm at the end of my ideas - Can somebody help me please - does someone hat an idea or a solution?

Thanks a lot,
regards robert

*Sorry for my english - I'm german!