Thank you for your reply.
The mini-Displayport to VGA dongle has the Dell label on it and was suggested by Dell specifically for my Dell laptop, so I already have the dongle provided by the manufacturer.
As mentioned before, I have the latest Dell updates for the BIOS and the latest Intel drivers.
In my office, I use a docking station with two screens attached to it and that works fine. Only some beamers using mini-Displayport to VGA are a problem.
Joris