On an install or reinstall there are motherboard chipset drivers that must be installed BEFORE installing device drivers.  If the chipset drivers were skipped that is probably the problem. 

On an install the sequence is (1) Install Windows (2) Install Dell Desktop System software (on applicable models), (3) Install motherboard chipset drivers (4) Install device drivers including video, sound, ethernet, etc. 

If the chipset drivers were skipped, install them, restart the PC and then after Windows starts install any missing device drivers. 

HERE is the Dell downloads and it has 3 downloads listed for the chipsets. 

There are 3 chipset downloads. I first tried AMT SOL/LMS which failed (unsupported hardware/os), then I tried AMT HECI and Chipset Software Installation Utility which installed without errors. So I thought the chipset drivers are installed and continued with the device drivers.

After your post I retried the AMT SOL/LMS and now it installs without errors. The "PCI-Serieller Anschluss" is ok now. But the "SM-Bus-Controller" is still unknown.

That is part of the Intel chipset.  The Intel chipset should have taken care of this.  Did you reboot after installing the Chipset drivers?

Now it works.

I choose driver update in the device manager and manually pointed it to c:\dell\r227558\all and then the drivers were installed.

Thanks.