I followed the guide at http://msmvps.com/blogs/clustering/archive/2004/10/06/15096.aspx to move my laptop from a domain to a workgroup.
One thing caught my eye, and that is: - There's still a ton of records in the registry with the SID from the domain user - Files in C:\windows\system32 have owner set to that SID.
Questions: - How can I fix the issue re: the registry, or should I just leave it as it is? - Re: ownership of files, should I leave them owned by the SID, or change it?
One option you could use would be to select the top level folder (if possible) right click > properties > security tab > advanced > remove the option the inherit permissions and remove all entries and add your new username > owner tab > set yourself as the owner > hit apply and wait.
All being well this should resolve your problem.