While there was no way to decrypt the files on my new XP install, Microsoft was able to confirm that my original plan, which I told to Circuit City when I took my computer in for repair, should be able to fix my old drive. Which it did. I've decrypted most of my files through my old XP install, now, so I have access to most of the stuff again (forgot a few files, gotta get those later).

I'm going to have a few choice words with Circuit City about their repair proceedures.