Win XP file encryption

OS : WIN XP PRO

There were encrypted files in the PC (d:\ drive)created with an user accounts in administrator group.
(User didn’t tell it) I joined the PC to Active directory.
Then encrypted files not accessible .
I removed the PC from AD and put it to workgroup and logged in using previous account.Still user can not open those files.
(unfortunately user don’t have any backup certificate)
Is possible to open these files ?