If you are talking about Windows 2000/XP file encryption, if you have not got the password, the data is gone forever. Unless you have a supercomputer and many decades of time.
This is why, when encrypting files or folders, it is a good idea to note the password somewhere and back up the certificate, because if the user account gets deleted or whatever, a new user account, even with the same name, will have a different and useless certificate.