This article click here explains how encryption
works and may be useful to you. It certainly explains in the paragraphs below why you can't access your files since you upgraded your OS. Sorry but I can offer no further advice on this subject but others may.
"Why must you be careful with EFS.
You need to be careful with EFS because if you lose your private key for decrypting data and haven't designated a recovery agent, you'll never be able to decrypt the data. That means in effect that you lose access to the contents of the encrypted files or folders forever.
Even if you don't lose your private key, system problems can effectively lose it for you. In particular, be aware that reinstalling Windows prevents you from accessing encrypted files.
Because reinstalling Windows creates accounts with different SIDs, you won't be able to access encrypted files directly, even if the account names are the same. Instead, you'll need to import your EFS certificate in order to be able to access encrypted files."