No you cannot upgrade from x86 to x64 via migration. It would basically be a reinstall because the binary files are different architectures. So you wouldn't gain anything anyway.
Furthermore the Program Files
folder in x86 is x86 apps but in x64 it is for x64 apps so Windows would have to "move" all the files. Unto itself that is easy but Windows would also need to search all possible locations where file paths may be stored including the registry, configuration files, etc and fix all those references. This is pretty much impossible in my opinion because Windows has no way of knowing that the .dat
file my app uses is a text file containing a hard coded path to the my installation location.
Yet another issue is with drivers. None of the x86 drivers would work either so the installer has to remove all the old drivers (and their files because System32
is x86 in x86 OS and x64 in x64 versions). As you can see this is a lot of work with a high risk just to save bringing up new hardward.
Finally I would say this is also a great time to upgrade the server HW to something newer. System reqs change and most likely the HW you had back that are minimal (or close to that) for new server OSes anyway.