microsoft.public.windowsxp.security_admin

Since you reinstalled Windows, the Certificate for the encrypted Folder is
lost and cannot be restored, even with the same username and /or password.
This means, the encrypted files are now junk unless you can get your hands
on the certficate, which I doubt.

The next time you encrypt a folder, export the certificate for that user
(yourself) and store it privately on a disk or USB drive to import it later
back into Windows to restore access to encrypted files.

There should be enough guides for exporting EFS-certificates found via
google.