How can I safely migrate an account from domain to standard local account ? I have a plenty of software installed within this account and I do not want to reinstall it again. I assume there are so many entries in registry that have to be preserved.
Like @Tim, I'm assuming you're talking about the user profile and not actually the account SID, since that's "fixed" and can't be "migrated".
The "official" tool provided by Microsoft for this purpose is the User State Migration Tool. It can be used to migrate local accounts to domain accounts.
If you're feeling particularly brave you can use one of a variety of unsupported methods, a couple of which I'll list here: