Adding an existing local user account to AD (Windows 10) [duplicate]

Solution 1:

Your domain account will create a completely new profile (new SID) on the computer so you will have to backup your old profile (Microsoft's User State Migration Tool (USMT) can help you do this - the proper way! - or, as Ramhound points out, you can do it the other way by taking ownership of the old profile and copying the files to a shared location - this is often what most people resort to doing but, be careful, if you need settings transferred then this won't do them (unless the settings are in files)) and then restore your files and settings to the new profile.

USMT can do the export and the import for you, given the right commands. It's a big beast so please do your research before diving in: https://technet.microsoft.com/en-us/library/hh824873.aspx