Dell does not officially support Win 10 on this model.  They only have XP and Vista drivers.  However, that does not mean its not compatible or marginally compatible as some old hardware is successfully running older versions of Win 10.  Microsoft did start excluding some older hardware with the 1803 version and that may be the problem.  If you can run a version older than 1803 it may work OK.    
I've recently had issues with my desktop ( XPS 420 ). For a while it has been fine. I've done a clean install and everything was fine, including adding drivers , etc ( it seems ). Then it downloads a further update ( NVIDIA driver update for NVIDIA GeForce 9800GT). It then states a restart is required to activate that update. At that point, it goes to a black screen and the screen enters power save mode. Is XPS 420 able to operate with Windows 10, or do i need to revert back to original OS ? Thanks
XPS 420 and Windows 10 version 1809