Bill - if you have the service tag for the Dell, that would help to check if you can upgrade the memory in place.
I would think seriously about pulling the drive, inset a new one, add RAM, and do a fresh OS install. Not destructive, and if you don't need the domain controller & other functionality; e.g. Just AC and shared files, you could do it on a Saturday.
We'll be installing at least 2 T420s this month, so it isn't like the hardware is past use.
