Anyway, now I cannot access my own files, because I did NOT backup a certificate or key or whatever it is (I don't know much about encryption). I don't remember ever being warned or informed about encryption by Windows, or being asked to create a certificate, so I must never have done so. Ok, it was obviously stupid to encrypt files without reading about it first, but I would expect Windows to warn people about it.
So, I need to decrypt these files without any authentication, basically! Surely there must be a way, as I have read about many other people faced with the same dilemma!
I may be able to recover my deleted "Documents and Settings" folder from the previous installation using a data recovery tool, would this make it any easier?