Although not officially a Dell supported update, our old XPS 420 easily updated from shaky and failing Windows Vista Home to Windows 10 Professional without any need for seeking out special drivers.
Lost the mini viewer and that was pretty much it. Easy!
The machine runs like new now, everything else works flawlessly, and thanks to the 64 bit upgrade, I splurged on some extra memory, going from 3 Gbs to 8 Gbs from Crucial after the operating system upgrade, again, no problems at all. *The first few boots though, I would swear the machine loaded slowly as Windows 10 tried to sort out if it was the same machine. Imagination? I don't know, don't think so though.
In all the years we have used this machine, we have never needed to replace a single factory component. I added a second hard drive a few years back for storage. Had this machine since April 2008.