Switching domains
I have a machine at home that's been my domain controller for years (since 1999 or so). I tried to make my new Dell SC420 with Windows Server 2003 installed the domain controller, but that turned out to be a real pain to do. The old box refused to replicate to the new one. I don't know why.
Rather than spending a lot of time figuring it out, I created a new domain. Easy enough, but the problem is my account (with all my documents and pictures and so on) is in the old domain. When I log into my desktop on the new domain, it's like I'm a brand new user.
Copying my documents and desktop over isn't so bad, but the HKEY_CURRENT_USER hive of the registry belongs to the old user; the new user gets a clean one. This is a pain, because I lose every setting in every application.
Even the File and Settings Transfer Wizard didn't really help me here - It transferred some of the Windows settings, but for most applications I'm still on my own.
I still have to figure out how to preserve my Windows Media Player metadata, since I've rated hundreds of songs and that data's in the old user's database. What a pain.
But on the plus side, and the goal of those whole operation, is that I can now turn off my old IBM P2/350 computer that's been doing little more than authenticating users and consuming power for the last 2 or 3 years.