PS: I am using Windows 10 and resolution 1280*1024
You will need two active adapters mDP-DVI as the W4100 can only support up to two passive display connections (HDMI/DVI) at one time. So the third and fourth display will need adapters.
Thank you for your quick answer Matt.
I could not see the card in the catalyst control center. The software was" empty". After talking with a Dell technician, he advised me to try unseat and re-seat the card which I did. Then I re-installed the software/drivers and now I can see all the options. While he told me that 4 passive were ok, I just bought 2 active as you said (the problem is/was maybe a mix of these two issues).