You will not be able to upgrade to a processor that is new enough for Windows 11. Windows 11 only supports Intel CPUs that are generation 8 or newer and I believe the best CPU for the 3420 is a 7th gen. Now it is possible to still install Windows 11 by downloading the media creation tool here for Windows 11. Using that method the CPU check is bypassed.
Hi, I have a SFF Precision 3420 with an Xeon(R) CPU E3-1240 v6 @ 3.70GHz 3.70 GHz processor.  This processor is not compatible with Windows 11 and I would like to upgrade to one that is.  Is that possible and if so, what processor is recommended/preferred? Rob
Processor upgrade for Dell Precision Tower 3420