Originally posted by mr. vb
You need the recovery key or the user certificate (with which the files were encrypted) from your old Win XP installation to decrypt files -- doesn't matter if you are an administrator.

What I would do now, if I were you, is export your recovery key to a floppy disk and put it somewhere safe so in case you need to re-install again, you will have access to your files.

mr. vb
I think you have to be the specific "Administrator" account from the installation used to encrypt the files :S