This definitely falls in the category of "You should know better."
I lost the domain controller on my home network a while back. I've been running my other computers (a desktop and laptop) without a DC since then, and it let's me login from the cached passwords. But this morning I brought the newly build domain controller online, and this evening I fired up my laptop. Well, of course, the new Active Directory service knows nothing about my old logins, and the laptop won't let me on.
So I go to the DC, and create the same user with the same password as before, but, I know, the security identifier's different, so the machine thinks it's a different users. After logging in to the local admin account on the laptop and joining the machine to the domain, I login as my regular domain user, and it creates me a new profile.
Well, of course, now I don't have access to any of my old files, and my local data is in the old profile.
So I logged in as local admin again, and granted permissions and ownership on my old C:/Users/dave directory to the new DOMAIN\dave user. And then, hoping to get my old profile back, I went into regedit and did a search for everywhere that it was pointing to the new profile directory (C:\Users\dave.DOMAIN) and changed it to point to the old one (C:\Users\dave). And then tried to login in.
I get "Group Policy Client service failed the login"/Access is denied.
I googled it, and found something about wiping out the profile by changing the Guid in the HKLM/Software/Microsoft/Windows NT/CurrentVersion/ProfileList, in hopes that it would create a new profile, but I think that may have made matters worse.
I still have admin access to the machine, so my data is not at risk, but short of backing up my data, reinstalling windows, and then copying the data back that I need, I can't seem to get on as me.
Thanks for rescuing me from my own foolishness.